Feb. x6,1934 
Physiological Studies on Flag Smut of Wheat 
439 
Table VII .—Results of inoculating wheat seedlings at three definite stages of growth with 
both soaked and dry spores of Urocystis tritici and planting them in the greenhouse at 
Arlington Experiment Farm , Rosslyn , Va., December g to 16, igzi 
Variety. 
Seedlings inoculated with— 
! 
Average 
Lot 1. 
Soaked spores. 
| Lot 2. Dry spores. 
percent¬ 
age of 
infection 
includ¬ 
ing both 
lots. 
Total 
plants. 
Infected plants. 
Total 
plants. 
Infected plants. 
SEED COAT JUST BROKEN. 
i 
j 
} 
i 
Number. 
Per cent . 
Number. 
Per cent. 
Bobs.. 
36 
4 
II. I 
35 
17 
48.6 
29.6 
Hard Federation. 
34 
5 
14.7 
33 
16 
48.5 
31-3 
Harvest Queen. 
32 
6 
18.8 
34 
6 
; 17.6 
18.2 
Little Club. 
3 1 
20 
64.5 
28 
IO 
35-7 
50.8 
White Federation. 
33 
20 
60.6 
30 
23 
I 76.7 
68.3 
plumule and three roots s 
i 
| 
DEVELOPED. 
! 
Bobs . I 
35 
5 
14.3 
34 
12 
35-3 
24.6 
Hard Federation.1 
35 
9 
2 5*7 
36 
II 
30.6 
28.2 
Harvest Queen. 
34 
10 
29.4 
33 
4 
12.1 
20.9 
Little Club. 
30 
25 
8 3-3 
3 1 
18 
58.1 
70*5 
White Federation. 
29 
18 
62.1 
29 
16 
55-2 
58.6 
COLEOPTILE broken. 
Bobs. 
35 
0 
O 
3 6 
0 
0 
O 
Hard Federation. 
36 
0 
O 
36 
0 
0 
O 
Harvest Queen. 
35 
0 
I ° 
34 
0 
0 
O 
Little Club. 
3 2 
0 
! 
! 0 
33 
0 
0 
O 
White Federation. 
control: 33 RY ungermi¬ 
! 
nated SEED. 
Bobs. 
17 
8 
47. I 
47. 1 
Hard Federation. 
17 
8 
47 * 1 
T-/ • 
47.1 
Harvest Queen.. 
15 
7 
46.7 
17 
9 
52.9 
5°.° 
Little Club. 
8 
8 
100 
8 
6 
75-o 
87*5 
White Federation. 
7 
5 
71.4 
1 
7 
5 
71.4 
71.4 
Abundant infection occurred in the plants inoculated at the first two 
stages, but in no case was there infection of any plant which was inocu¬ 
lated after the coleoptile was broken. The highest percentage of infection 
in the three-root stage was 83.3 per cent in Little Club, and in the stage 
where the seed coat was just broken there was 76.7 per cent in White 
Federation. There apparently was no relation between the condition 
of the inoculum at time of application and the percentage of infection 
produced in each case. In some instances where the inoculations were 
made at the same stage of growth the dry inoculum produced a higher 
percentage of infection, while in others the spore suspension produced 
the higher percentage. Four of five varieties had higher percentages 
of infection when inoculated with dry spores at the time the seed coat 
was just broken than when the inoculations were made at the three-root 
stage. All of the varieties inoculated with the spore suspension had 
higher percentages of infection when they were inoculated at the three- 
root stage than when the seed coat was just broken. In the varietal- 
resistance experiments herein described infections of 100 per cent were 
