Aug. is, 1914 
Head Smut of Sorghum and Maize 
355 
Table II .—Results showing the effect of various hot-water and modified hot-water treat¬ 
ments on the viability of the spores of the head-smut organism --Continued 
Treatment. 
Duration 
of test. 
Number 
counted. 
Serial No. 
Duration. 
Temper¬ 
ature. 
Duration of 
presoaking. 
Germination. 
Mtn. 
0 C. 
Hours . 
(«) 
Days. 
f 2 
Per cent . 
0 
31 
20 
60 
{ 8 
O 
32 
Control. 
6 
{ 8 
950 
4-5 
No increase. 
0 
60 
f 2 
33 
IO 
6 
l 8 
0 
60 
f 2 
0 
34 
20 
6 
{ 8 
0 
35 
Control. 
(“) 
/ l 
13.1 
Slight. 
Slight. 
f 70 
\Dry heat. 
36 
5 
> . . .. 
f 
l 6 
» Not soaked. 
In the tests of the effect of fungicides on the spores the solutions of 
different strengths, including water for control, were prepared at a 
temperature of 22 0 to 23 0 C. and placed in culture tubes. The spore 
material was prepared as for the thermal tests and transferred to the tubes 
in the same way. The culture tubes were then thoroughly shaken. At 
the end of the period indicated in the tables the tubes were again agi¬ 
tated and with a pipette 5 c. c. were removed from each to the centri¬ 
fuge tubes, which were immediately filled with water. The spores being 
thrown down by centrifuging, the water was poured off and the tubes 
refilled, this rinsing being repeated four or five times. The last rinsing 
water from the strongest treatment was poured on to the control, which 
was then recentrifuged, to make certain that the rinsing had removed 
the treating solutions effectively. Further water being added, enough of 
the suspension of spores was poured into a tube of melted carrot agar 
at about 43 0 C. to make a thickly seeded plate. The plate was poured 
immediately, incubated, and examined as in the other tests. 
In the work with copper sulphate, solutions equivalent to from 
0.35 per cent to 2.52 per cent of CuS0 4 were used in treatments of 
sorgo seed, some of which had had the glumes removed before treat¬ 
ment. In one series (1907) a 17-hour soak with the weakest of these 
solutions gave plants with 2.3 percent infection as against none in the 
controls, while in another series (1911), using seed without glumes, a 
10-minute treatment with the strongest solution resulted in 13.1 per cent 
of infected plants as against 2.8 per cent in the controls. 1 Other treat- 
1 The fact that all of these treatment experiments, except the modified hot-water treatments, were also 
infected by Sphacelotheca sorght seems to have had a peculiar bearing on these comparative percentages. 
In nearly all cases a considerably larger amount of head smut occurred in the treated lots than in the con¬ 
trols, which, not having been treated, were heavily infected by the kernel smut. The latter seemed to 
get the start of the head smut and prevent its development, for no case of evident double infection, as was 
observed by Busse (1904, p. 381), was found. Thus, in the various treatments of Red Amber sorgo carried 
out in 1911 with formalin, cresol, copper sulphate, and hot water, 24 treated lots containing 3,616 plants 
averaged 10 per cent of head-smut and 2.6 per cent of kemel-smut infection, while 15 lots (3,081 plants), 
untreated or unsuccessfully treated for the kernel smut, contained 5.8 per cent of head smut as against an 
infection of 29 per cent by the kernel smut. One lot with 62.3 per cent of kernel smut had 3.3 per cent of 
head smut; in another the percentages were 57.1 and 1.8, respectively. This phenomenon seems to have 
an adequate explanation in the comparatively late period of Infection shown for the head smut (see p. 365). 
