Aug. 15, 1914 
Head Smut of Sorghum and Maize 
359 
Table IV .—Summary of results showing the influence of locality on the occurrence of 
head smut 
Percentage of infection at— 
Seed from— 
Amarillo, Tex. 
j Chillicothe, 
i. 
Tex. 
I 
St. Paul, Minn, j 
Arlington, Va. 
1910 , 
1911 
1912 
1910 
1911 
1912 
1910 
1911 
i 
1912 
1910 
1911 
1912 
Amarillo, Tex. 
1. 6 
14- 71 
13-09 1 
17- i4 i 
7*56 
10. 86 
0.14 
’25 \ 
0 
j 
7-34 
6- 93 
3- 52 
4. 46 
0 
0 
0 1 
0 
0 
0 
Chillicothe, Tex. 
3 
12. 29 
1. 72 
2.9 
0 
0 
0 
o j 
0 
0 
0 
St. Paul, Minn. 
.87 
2.6 
0 
0 i 
0 
0 
Arlington, Va. 
0 
0 
0 
o 
From this it may be seen that no infection occurred at Arlington or at 
St. Paul. Only a trace of it has ever occurred at St. Paul, except in 
inoculated plants in 1912. It has not been present at all at the Arlington 
Experimental Farm or in its immediate vicinity during the three years 
in question, so far as the writer was able to discover by careful exam¬ 
ination. Yet seed from St. Paul produced the highest percentage re¬ 
corded at Amarillo in 1911, although showing no infection at either 
Arlington or St. Paul in that year; and seed from Arlington has always 
produced some smutted plants at the two Texas points. Of the four 
seed lots used in 1911, the Arlington seed produced the largest number of 
infected plants at Chillicothe. Moreover, seed grown at either of the 
two Texas stations never produced smutted plants when grown at the 
other two stations, although inoculated plants showed abundant infection 
at St. Paul in 1912 (see Table V, plat E). It should be noted, too, that seed 
from the same lots .used for the Amarillo plantings in 1910 and 1 911 were 
planted at Amarillo in the ensuing years and produced infected plants 
as follows: 1910 lots, replanted in 1911, 3.8 per cent and 15.6 per cent, 
respectively; 1911 lots, replanted in 1912, 1.8, 2.7, o, and 1.8 per cent, 
respectively. These figures are evidently in no way comparable or con¬ 
sistent with those of the year before, as shown in Table IV. 
EXPERIMENTS WITH PROTECTED SEED 
As may have been already observed, particularly in connection with 
the slight irregularities of the curves in figure 6 (see footnote, p. 351), 
positive conclusions from comparative amounts of infection in small lots 
of plants at Amarillo are not warranted without consistent results from 
oft-repeated experiments. However, the appearance of any infection in 
plants from seed protected from contamination gives additional evidence 
that the infection is not carried with the seed. 
Thus, 177 plants were grown at Amarillo in 1912 from seed produced 
in the greenhouse at Washington, D. C, on heads which had been covered 
with transparent paper bags from before flowering until they were 
thrashed out by hand. One plant (0.6 per cent) was infected. Simi¬ 
larly, 1.669 plants grown in 1912 from seed of 18 heads protected in the 
