284 Ward . — On Relations between Host and Parasite 
TABLE XIII. 
Exp. No. 707, June 8, 1901. ‘ Seed’ sown June 1. Seedlings germinated in inter- 
mediate pit one week, then infected at tips and kept under glass 48 hours. 
Then outside under glass, in damp shady comer. Very damp and drawn plants. 
Species. 
Origin of 
spores. 
Results. 
Approximate 
No. of seed- 
lings infected. 
Incubation 
period. 
No. of leaves 
with pustules 
on 16 th day. 
Period of 
observation. 
B. mollis (1) 
B. mollis 
+ 
20 
io days 
2 
21 days 
99 
B. sterilis 
— 
20 
0 
99 
B. velutinus 
B. mollis 
— 
20 
0 
99 
99 
B. sterilis 
— 
20 
0 
99 
B. maximus 
B. mollis 
— 
20 
0 
99 
,, (2) 
B. sterilis 
+ 
20 
13 „ 
1 
99 
B. sterilis 
B. mollis 
— 
20 
0 
99 
„ ( 3 ) 
B. sterilis 
+ 
20 
10 „ 
10 
99 
B. madritensis 
B. mollis 
— 
20 
0 
99 
99 
B. sterilis 
+ 
20 
10 „ 
3 
99 
B. erectus 
B. mollis 
— 
IO 
0 
99 
99 
B. sterilis 
— 
IO 
0 
99 
B. commutatus 
B. mollis 
— 
20 
0 
99 
99 
B. sterilis 
— 
20 
0 
99 
B. arvensis 
B. mollis 
+ 
12 
16 „ 
2 
99 
99 
B. sterilis 
— 
12 
0 
99 
B. secalinus 
B. mollis 
+ 
8 
16 „ 
2 
99 
99 
B. sterilis 
— 
10 
0 
99 
B. interruptus 
B. mollis 
— 
20 
0 
99 
99 
B. sterilis 
— 
20 
0 
99 
B. racemosus 
B. mollis 
— 
10 
0 
99 
99 
B. sterilis 
- 
10 
0 
99 
(1 ) 11 other leaves have spots not burst, owing to drying up of tips. 
( 2 ) Perhaps doubtful ? ( 3 ) Several other leaves show spots. 
mosus as they did in the previous experiment. As before, 
B. sterilis , B. madritensis , B. maximus , B. erectus , B. commu- 
tatus , and B. interruptus seemed to resist the fungus. 
Again, we see that the spores from B. sterilis readily infect 
in B. sterilis and B. madritensis , but not others, except in the 
doubtful case of B. maximus. 
This series undoubtedly raises questions as to how far the 
physiological condition of the host affects the question of 
infection, a question to which I shall return subsequently. 
In another series, Table XIV, the seedlings were raised 
as in the previous series, and the infected plants were kept 
in the laboratory at a west window under damp bell-jars. 
Thus the general temperature was considerably higher than 
