May, 1922; 
RAINES — VEGETATIVE VIGOR OF THE HOST 
231 
higher incidence of infection in the vigorously growing plants of group F 
and have converted it into an apparently lower susceptibility. It is notice- 
able that the pustules were larger in experiment V than in the other four 
experiments. 
Variation in the Incidence of Rust Infection with Variation in the Growth 
Vigor of the Host Plant, due to Constitutional or Racial Differences 
In soil-culture experiments IV and V, when the 100 variables of each 
group were arranged in the order of their dry weight, the series divided 
into five equal parts of 20 variables each, and the average weights and 
degrees of infection of these sub-groups determined, a certain relation was 
apparent between the relative weight attained by a plant and the incidence 
of rust infection on it. The figures obtained in this analysis of the data 
are presented in table 13. 
Table 13 
Experiment I V 
Mean Dry Weight of Tops of 
Plants in Mg. 
Mean Infection per Unit Area of most 
Severely Infected Leaf of Plant 
Group 
Sub-groups 
First . 
Second 
Third 
Fourth 
Fifth 
First 
Second 
Third 
Fourth 
Fifth 
A.... 
40 
65 
no 
148 
239 
2.3 
2.4 
1.8 
2.0 
1.6 
99 
129 
148 
172 
231 
2.8 
2.1 
2.9 
3-5 
2.1 
B.... 
99 
140 
179 
231 
345 
2.3 
2.9 
2.5 
2.1 
1.8 
D.... 
90 
144 
182 
231 
363 
3-6 
3-0 
2.5 
3-9 
2.9 
C... 
141 
233 
336 
430 
596 
4.0 
3-0 
2.3 
4.4 
1-7 
F.... 
305 
555 
653 
812 
4-7 
57 
5-2 
3-8 
3-3 
129 
193 
252 
311 
431 
3-3 
3-2 
2.9 
3-3 
2.2 
Experiment V 
Mean Dry Weight of Tops of 
Plants in Mg. 
Mean Infection per Unit Area of most 
Severely Infected Leaf of Plant 
Group 
Sub-groui 
First 
Second 
Third 
Fourth 
Fifth 
First 
Second 
Third 
Fourth 
Fifth 
A.... 
21 
34 
43 
54 
83 
II. 8 
13.6 
II-5 
II.6 
9-3 
B.... 
22 
36 
50 
65 
92 
12.3 
14.0 
II. 7 
12.2 
8.6 
£.... 
42 
67 
85 
■ 108 
159 
15-9 
12.2 
11.9 
8.6 
7.8 
C 
53 
71 
88 
106 
148 
10.2 
10. 0 
II. 0 
8.6 
7-4 
D.... 
47 
72 
90 
107 
162 
12.0 
13.2 
10.5 
8.0 
7.2 
F.... 
190 
283 
349 
416 
558 
9.9 
6.8 
7.2 
7-7 
6.2 
63 
94 
118 
143 
200 
12.0 
11.6 
10.6 
9-5 
7.8 
The figures show that there was considerable variation in the growth 
