6 BULLETIN 336, U. S. DEPARTMENT OF AGRICULTURE. 
Table II. — Annual and average mean, maximum, and minimum temperatures, by 
months, at Washington, D. C. — Continued. 
1909 
1910 
1911 
1912 
1913 
Average. 
Month. 
$ 
3 
.s 
& 
a" 
d 
S3 
03 
3 
S3 
03 
& 
.5 
3 
pi 
03 
« 
& 
Pi" 
i 
pi 
3 
d 
a 
Pi 
i 
Julv 
74.7 
73.0 
66.4 
53.1 
96 
96 
84 
80 
77 
66 
53 
53 
42 
31 
29 
8 
77.6 
73.8 
71.0 
60.2 
41.4 
30.5 
95 
90 
94 
90 
66 
62 
57 
58 
48 
31 
23 
8 
78.7 
76.6 
70.4 
57.2 
42.8 
41.0 
99 
100 
89 
80 
70 
67 
56 
54 
46 
38 
22 
22 
75.8 
73.4 
70.4 
59.3 
46.9 
40.0 
94 
92 
94 
87 
77 
73 
60 
53 
42 
36 
25 
19 
77.6 
74.2 
67.4 
58.8 
47.8 
40.4 
97 
97 
93 
77 
76 
66 
58 
54 
40 
35 
28 
24 
76.4 
73-9 
69.0 
56.7 
45.6 
36.4 
35.6 
33.4 
43.2 
54.2 
64.7 
71.8 
55.1 
95.1 
93.7 
90.3 
83.7 
71.9 
65.9 
65.5 
62.7 
77.9 
85.2 
90.4 
95.0 
56 6 
54.5 
42.9 
32.7 
24.5 
15.5 
September 
November 
December 
50.8 
31.8 
1910 
1911 
1912 
1913 
1914 
33.7 
34.7 
51.2 
57.9 
61.5 
69.7 
54.9 
58 
68 
86 
92 
87 
94 
*96" 
11 
8 
26 
37 
39 
45 
38.2 
37.0 
41.0 
51.2 
70.0 
73.0 
68 
68 
75 
80 
96 
101 
ioi' 
15 
21 
14 
26 
37 
56 
25.0 
31.0 
40.9 
55.6 
65.1 
70.4 
58 
56 
76 
81 
90 
93 
166" 
-13 
7 
18 
31 
41 
45 
43.6 
36.4 
49.0 
55.4 
64.4 
72.8 
68 
68 
77 
86 
90 
96 
"C6 _ 
24 
13 
17 
32 
37 
45 
38.6 
30.1 
29.4 
53.5 
67.0 
75.9 
55.1 
72 
59 
75 
86 
95 
98 
'98~ 
7 
-1 
15 
28 
41 
56 
8 7 
8 5 
March 
April 
19.5 
■>8 8 
38-3 
-19 8 
Annual: 
Mean 
Maximum . . 
55.4 
54.6 
57.3 
Minimum. 
8 
8 
-13 
13 
-1 
Table II shows that the highest average mean temperatures have 
been recorded in July and the lowest average means in February. 
The average mean temperature for the 10 crop years was 55.1° F. 
The variation from this average has been slight, the warmest crop 
year having an annual mean of 57.3° and the coolest 52.9°. During 
the 10 years the absolute maximum has exceeded 100° F. only once, 
and the absolute minimum has fallen below zero in only three years. 
The lowest temperature recorded during the period was in January, 
1912, —13° F. The annual mean temperatures at College Park are 
almost invariably 1 degree lower than at Washington. 
NATURE OF THE EXPERIMENTS. 
The primary object in all the varietal tests at College Park and 
Arlington Farm has been to determine the relative yieldmg power of 
the different varieties. Attempts have been made also to improve 
the yield, quality of grain, and other important characters in some 
of the leading varieties by both mass and pure-line selection. The 
production of new varieties by hybridization also has been attempted. 
The work done along these latter lines has been too extensive to per- 
mit presentation within the limits of this bulletin. 
Nursery experiments in which each variety is grown in short rows 
of uniform length, row space, and rate of seeding are also conducted, 
in addition to the regular varietal tests in field plats. The usual pro- 
cedure has been that if a new variety is especially promising in the 
nursery it is advanced to the field-plat tests as soon as sufficient seed 
