46 
BULLETIN 1284, TJ. S. DEPARTMENT OF AGRICULTURE 
seeds of each variety were used and the temperatures ranged from 
27° to 29° and 30° to 32° C. The rate of growth was naturally 
greater at these temperatures. The same general behavior among 
the varieties was noted in these experiments as was indicated in 
Table 13. 
If the rate of germination is correlated with varietal resistance, 
one should be able, perhaps, to produce infection in resistant varieties, 
like feterita, by reducing the temperature, which in turn would 
retard the rate of germination. Such conditions undoubtedly occur 
frequently in nature, but these varieties have maintained their re- 
sistance under all conditions in the field. 
The percentages of infection obtained at Columbia in 1918 were 
very much lower than those secured during the two previous years. 
Plants of certain varieties were grown from the same original lot 
of seed during 1916, 1917, and 1918. The results are presented in 
Table 14. It will be noted that the percentages of infection for 
1918 are invariably lower than those obtained during 1916 and 1917. 
In fact, varieties that had been shown by the work of the previous 
years to be highly susceptible gave very low percentages of infection 
in 1918 and in a few cases gave negative results. In a number of 
additional varieties plants were grown from the same seed lot in 
1917 and 1918, and the percentages of infection in 1917 were invari- 
ably higher than in 1918. 
Table 14. — Infection of sorghums with covered kernel smut at Columbia, Mo., in 
1916, 1917, and 1918 
Seed 
serial 
No. 
1916 
1917 
1918 
Group and variety 
Plants 
Infec- 
tion 
Plants 
Infec- 
tion 
Plants 
Infec- 
tion 
Shallu 
46 
47 
48 
52 
54 
50 
23 
24 
26 
40 
39 
33 
34 
36 
30 
32 
Number 
113 
416 
309 
193 
253 
259 
446 
545 
321 
194 
203 
178 
191 
318 
289 
267 
Per cent 
52.2 
19.7 
16.5 
14.5 
18.6 
28.2 
24.2 
36.3 
40.8 
10.8 
24.6 
53.9 
44.5 
36.2 
54.0 
37.1 
Number 
63 
94 
226 
103 
113 
111 
109 
115 
120 
114 
108 
112 
106 
100 
110 
88 
Per cent 
71.4 
23.4 
21.2 
10.7 
42.5 
37.8 
31.2 
23.5 
29.2 
14.0 
27.8 
68.8 
68.9 
49.0 
38.2 
3.4 
Number 
84 
107 
101 
137 
56 
55 
87 
82 
68 
77 
69 
95 
49 
47 
59 
101 
Per cent 

Sorgo: 
Collier 
1.9 
Dakota Amber . 

Minnesota Amber . 
Kansas Orange. .. 
2.9 

Dwarf Ashburn. .... 

Broomcorn: 
Standard ■ 
1.1 
Do 
6.1 
Do 
11.8 
Kaoliang: 
Brown _ .. 
5.2 
Manchu_ _. _.___ 
4.3 
Kafir: 
Blackhull 
7.4 
Do 
2.0 
Red 
10.6 
Durra: 
Brown _ . ... 
13.6 
White 

The low infection percentages obtained in 1918 perhaps may be 
correlated with the high temperature and low precipitation during 
the planting season. Table 15 shows the mean daily temperatures 
and the total precipitation for the seven days prior to seeding, includ- 
ing the day of seeding, and for the seven days following the seeding 
of the sorghum. 
