Brown. — Studies in the Physiology of Parasitism . VIII, 1 1 5 
petal from which they had been taken. Side by side with these readings 
the petals were closely examined for the first macroscopic appearance of 
infection, i. e. for the presence of small discoloured spots or, what was 
found to be a better test, for the presence of small translucent patches when 
the petals were viewed by transmitted light. In this way the progress of 
infection was studied side by side with the rate of exosmosis into the 
drops. The following table gives the results obtained in one particular 
experiment : 
An * denotes that in the intervals so marked infection could be seen to have begun. 
Conductivity at the following intervals fro?n sowing : 
Spore-free 
drops . 
Spore-con- 
taining drops. 
5 hrs. 
6 hrs. 
7 hrs. 
8 hrs. 
9 hrs. 
I. 
2-17 
3.81 
5*73 
6.64 
7-99 
2. 
2.30 
4-16 
5-29 
6-29 
6.98 
3- 
2-38 
4.21* 
5*58 
6-64 
7-54 
4- 
2.44 
4-16 
5- 2 9 
6-05 
6-84 
5- 
2-48 
4.21 
5*39 
6-26 
6.89 
6. 
2.48 
4*31 
5-4i 
6.31 
7.18 
7- 
2-48 
4.66 
6-29 
6.58 
7.67 
8. 
2-55 
3-87 
5.22 
6-03 
6-89 
9- 
2-82 
4.84 
• 6-45 
7*51 
8-55 
10. 
2.82 
5.04 
6.84 
7*34 
8-05 
1 1. 
2-89 
4.58 
5*9 2 
6-92 
7.64 
12. 
2.99 
493 
6.56 
7.61 
8-94 
I 3- 
3.21 
5-° 8 
6-21 
7.21 
8-02 
J 4* 
3*37 
4-60 
5-77 
6-86 
7-58 
1. 
2.18 
3.61 
4*9° 
6.25 
8.48 
2. 
2-32 
3-95 
5.20 
6-39 
8-35 
3- 
2.36 
3*95 
5* 18 
6-48 
8.32 
4- 
2.50 
3*64 
*6.78 
I 9*35 
4 Is 4 T 
5- 
2*69 
4*45 
6.23 
*9-°3 
13.96 
6. 
2.92 
4*45 
*3.72 
6-64 
8-o8 
J • 
3*°6 
4-73 
*6.31 
9*37 
18-76 
8. 
3.09 
4-64 
*6-34 
8-45 
12-57 
9- 
3.16 
4.49 
5.80 
6-86 
8.18 
10. 
3.28 
4.82 
6.16 
7.04 
7*99 
11. 
3-83 
5-9° 
*8-45 
13-77 
23.42- 
12. 
3.89 
6-34 
*11-10 
19-54 
3i-57 
*3- 
3-99 
5-9° 
*9-59 
18.76 
3W° 
! 4 . 
4‘5i 
*7.89 
17.66 
33*75 
— 
At the end of five hours from sowing no attack was visible in any 
case on macroscopic examination. At this time the average conductivity of 
the fourteen drops which contained spores was 3-11, that of the controls 2-67. 
The initial conductivity of the spore suspension was 1-3, that of water 0-9. 
Making this correction it is seen that the difference in rates of exosmosis in 
the two cases is negligible. 
Throughout the whole series it is seen that the rate of increase in 
conductivity is very similar in the spore-containing drops to that in the 
controls until such time as infection was seen to have occurred. When this 
happened the conductivity of the spore-containing drops in general rapidly 
rose to high values, the surface of the petal in contact with the drop 
becoming in the meanwhile entirely discoloured through the coalescence 
K 2 
