138 
AMERICAN JOURNAL OF BOTANY 
[Vol. io, 
At this latter date they were transferred to the warm-temperature house, 
the soil having first been brought to the moisture content desired for the 
experiment. 
Table 3 
Moisture, Percent 
No. Plants 
No. Diseased 
No. Dead 
14-16. 
4 
1 
0 
16-18. 
4 
4 
1 
23-24 . 
4 
4 
3 
26-28. 
4 
4 
3 
31-33 . 
4 
4 
4 
35 (saturation). 
2 
0 
0 
On March 15 the experiment was concluded, and the data taken are 
shown in table 4. 
Table 4 
Moisture, Percent 
No. Plants 
No. Diseased 
No. Dead 
13-14 . 
4 
0 
0 
15-16. 
4 
1 
1 
17-18. 
2 
2 
0 
22-24. 
4 
4 
3 
26-28. 
2 
2 
1 
28-32. 
3 
3 
3 
35 (saturation). 
2 
0 
0 
These experiments showed that the plants growing in the driest possible 
soil were highly resistant to the wilt disease in spite of the fact that these 
plants wilted badly during the middle of the day from lack of water. The 
most rapidly growing plants were attacked and killed first, while plants 
growing in saturated soil seemed immune since they were never attacked 
by the disease. During the progress of these experiments data were taken 
on the incubation period of the disease under the different conditions of 
soil moisture. The data given in table 5 are from experiment IV. 
Table 5. 
Moisture, No. Days Prior to First Incubation Period 
Percent Appearance of Disease (Average) 
13-H. 35 35 
15-16. 24 24 
17-18. 26 26 
22-24. 15 19 
26-28. 18 20.5 
28-32. 15 19 
35 (saturation).. — — 
These data again bring out the point that the disease makes its most 
virulent development with medium and high soil moisture. The plants 
growing in dry soil were slow to produce visible signs of the disease, and 
the development of the trouble, even after it had affected the lower leaves, 
was very much retarded. 
