Feb. 16, 1924 
Physiological Studies on Flag Smut of Wheat 
435 
Table IV. —Infections of Little Club wheat produced by spores of Urocystis tritici buried 
at different depths and for varying periods during the winter of IQ22-23 at the Missouri 
Botanical Garden , St. Louis, Mo. a 
Average 
depth spores 
were buried. 
I. 
! Date when spores were— 
f 
j 
! Total 
: number of 
1 plants. 
i 
j 
Infected plants. 
1 
| Buried. 
Exhumed. 
Number. 
Per cent. 
1 
j Inches. 
I 
i 
j Control.. 
22 
21 
95-5 
89.3 
i 2 
1 Nov. 28 
Jan. 4 
| 28 
i A A 
! 25 
! 6 
2 5 
1 2 5 
IOO 
! 2 
Dec. 2 
. . . .do. 
19 
i 
IOO 
: 6 
....do. 
. .. .do. 
27 
27 
IOO 
! 2 
Dec. 6 
-do. 
8 j 
: 8 
IOO 
| 6 
... .do. 
-do. 
24 | 
20 
83.3 
; 6 
Nov. 24 
... .do.j 
25 i 
24 
96.0 
1 2 
_do. 
Feb. 3 ; 
24 ; 
6 
25.0 
} 6 
....do. 
... .do.I 
23 
12 
52.2 
2 
....do. 
Feb. 18 ; 
26 ! 
5 
19.2 
6 
....do. 
Feb. 22 ! 
22 
6 
27.3 
2 
-do. 
Mar. 1 
18 j 
3 
16. 7 
6 
... .do. 
20 i 
0 
0 
2 
-do. 
Mar. 16 1 
18 
0 
0 
6 
....do. 
... .do.j 
18 ! 
2 
11.1 
2 
-do. 
Apr. 14 | 
18 j 
0 
0 
6 
_do. 
....do. 1 
I 
1 
18 
0 
0 
0 Experiments in cooperation with the Missouri Botanical Garden. 
On October 5, 1921, a plot of land about 10 feet square, near the ex¬ 
perimental field at Granite City, Ill., was inoculated thoroughly with 
flag-smut spores by spading under heavily infected wheat straw. On 
October 12, 1922, over one year later, clean seed of Harvest Queen 
wheat was sown in this plot. An uninoculated control plot of equal size, 
located some distance away, also was sown with uninfested seed of the 
same variety. In May, 1923, there were nine infected plants, or 2.4 
per cent, in a total of 377 in the inoculated plot. None of the 370 plants 
in the control plot was infected. 
Thus it has been shown that, though there is a decrease in viability, 
the spores are able to survive a winter and subsequent summer in the 
flag-smut area near St. Louis, Mo. They not only are capable of germina¬ 
tion, but actually can infect wheat plants. 
INFECTION 
Regarding the infection of wheat by Urocystis tritici , McAlpine (9) 
states: “Infection occurs in the seedling stage, also when the young 
shoots are being formed, but not when the plant is above ground, . . .” 
He proved that infection did occur in the seedling stage, but based his 
conclusions concerning the infection of new shoots as they are formed 
during tillering, on some data given by Hecke (3). The latter cut back 
to the collar shoots of sound plants of the perennial rye (Secale montanum) 
in the autumn. He then dusted spores of Urocystis occulta on the exposed 
collar and covered the plant with manure containing the same kind of 
spores. In the spring the shoots produced were infected. Discussing 
Hecke’s data, McAlpine says: “But a fresh light has been thrown on the 
infection of rye, and the same probably applies to wheat. By the ex¬ 
periments of Hecke ... it was there shown that the spore has not only 
