Dec. 10, 1917 
Flaxwilt 
583 
Table; I .—Results of artificial inoculations of resistant and susceptible flax plants with 
Fusarium Uni 
Date. 
Strain of flax. 
Number of 
plants in¬ 
oculated. 
Number of 
field plants 
infected. 
Number of 
greenhouse 
plants in¬ 
fected. 
I 9 I S- 
August 7. 
Resistant. 
7 
0 
Do. 
Susceptible. 
6 
0 
August 17. 
Resistant. 
A 
O 
Do. 
Susceptible. 
L T 
2 
2 
Do. 
.do. 
"3 
x 
August 26 . 
Resistant. 
O 
C 
0 
O 
Do. 
Susceptible. 
J 
r 
0 
Do. 
.do. 
D 
C 
0 
November 29. .. 
Resistant. 
O 
II 
O 
Do. 
Susceptible.. 
I 
I 
Do. 
.do. 
IO 
■2 
1916. 
O 
November 26,. . 
Resistant. 
I c 
0 
Do. 
Susceptible. 
*5 
13 
Since no infection was obtained by inoculating plants of the resistant 
strain, while those of the susceptible strain did become infected, it seems 
that there must be some immediate reaction on the part of the protoplasm 
of the resistant plant to check invasion by the fungus. 
Whatever the nature of resistance, it is not manifested to the highest 
degree unless the plant is kept under perfectly normal conditions. This 
fact was shown by the way in which seedlings of the resistant strain of 
flax were killed by the fungus in tube cultures (PI. 44, A, d), and was 
further tested by planting disinfected seeds of both the resistant and 
susceptible strains in flasks of soil which had been sterilized and inocu¬ 
lated with F. Uni. When these flasks were plugged with cotton and kept 
in the laboratory, the resistant strain of plants showed slightly more 
resistance at first, but later succumbed to the attack. However, when 
flasks were prepared as above and placed in the greenhouse without the 
cotton plugs, some of the plants of the resistant strain lived to the flower¬ 
ing stage, while plants of the susceptible strain immediately died of wilt. 
Even under greenhouse conditions, where the temperature runs above 
normal, some of the plants of the resistant strain wilt. 
Careful examination of the root system of resistant plants grown in 
infected soil showed that some of the smaller roots were decaying and 
there were brownish spots on the larger roots. A number of these plants 
which showed no signs of wilt above ground were taken and the root sys¬ 
tem disinfected thoroughly on the surface with a 1-to-1,000 solution of 
mercuric chlorid for 2 l / 2 to 5 minutes. They were then washed thoroughly 
and plated out on potato agar. In a large percentage of cases pure 
cultures of F . Uni were obtained from these roots. In some cases other 
