Dec. io, 1917 
Flaxwilt 
601 
Table IX .—Resistance to flax wilt of the first generation from individual crosses between 
resistant and susceptible strains of flax 
Parent strain. 
Date of 
planting. 
Num¬ 
ber of 
plants 
grown. 
Ratio at end of 
three weeks. 
Ratio at end of 
experiment. 
Num¬ 
ber of 
plants 
killed 
by 
wilt. 
Wilted. 
Not 
wilted. 
Wilted. 
Resist¬ 
ant. 
1916. 
4D30 (Fj). 
Feb. 2 
18 
0 
18 
0 
18 
0 
4D8 (Ft). 
.. .do_ 
36 
0 
36 
15 
21 
4 
Resistant No. 4. 
...do.... 
V 
18 
0 
18 
0 
18 
0 
Controls: 
Susceptible No. 3. 
...do- 
18 
5 
13 
17 
1 
13 
4D21. 
Mar. 29 
6 
1 
5 
6 
0 
1 
4D38. 
...do.... 
22 
6 
16 
7 
1$ 
3 
‘+■^0 . 
4D37.. 
...do.... 
32 
17 
13 
32 
0 
26 
. 
4D2O. 
...do.... 
0 
. 21 
16 
< 
21 
0 
20 
4D26. 
.. .do.... 
16 
Q 
7 
16 
0 
12 
4D32. 
., .do.... 
17 
7 
Q 
8 
17 
0 
17 
4D-mix. 
.. .do.... 
88 
7 
32 
36 
82 
6 
60 
Resistant No. 4. 
...do.... 
03 
J 
3 
00 
8 
87 
6 
Susceptible No. 3. 
...do_ 
a* 5 
85 
J 
80 
7 
5 
85 
0 
85 
4D36 . 
May 13 
16 
6 
10 
6 
10 
6 
4D31..... 
...do.... 
20 
0 
11 
10 
10 
6 
4D22 . 
.. .do.... 
20 
7 
IC 
13 
s 
11 
4D-mix. 
.. .do.... 
40 
J 
%2 
8 
36 
4 
26 
Resistant No. 4. 
.. .do.... 
63 
V 
7 
56 
26 
47 
4 
Susceptible No. 3. 
0 
75 
74 
1 
75 
0 
75 
6E2. 
Apr. 25 
6 
1 
5 
3 
3 
1 
4E8. 
...do.... 
8 
3 
4 
4 
2 
.. .do.... 
3 
0 
4 
I 
3 
0 
3 
4E6. 
...do.... 
10 
7 
3 
0 
1 
4 
..*. 
Resistant No. 4. 
.. .do.... 
10 
0 
10 
7 
1 
9 
0 
Susceptible No. 5. 
...do- 
5 
4 
1 
5 
0 
5 
However, it seems that there is a possible explanation for the results 
obtained. The resistant strain of flax has been bred by selection to 
resist wilt under certain environmental conditions which we might call 
normal. As was pointed out in Table III, resistance is probably due to 
a number of factors. Then it might be assumed that under the normal 
environment certain factors, A, B, C, for example, are required to pro¬ 
duce resistance. These factors, which may be of equal or unequal value 
in producing resistance, are possibly homozygous, as is evidenced by the 
fact that segregation is exceptional under what is termed a normal 
environment. If, however, the environment is made more severe, there 
is a certain amount of segregation among plants of the resistant strain, 
which was found to be true with plants growing in the greenhouse in the 
summer. Under these more severe conditions one or more additional 
factors, D, E, etc., might be supposed to be required to cause the plant 
to resist. Since the strain has not been selected to resist under these 
severe conditions of environment, no attempt has been made to make 
these factors homozygous; therefore they may be absent entirely, or 
may occur singly or in combination, and may be either homozygous or 
