Dec. io, 1917 
Flaxwilt 
591 
given with this stage of the plant as a starting point. It would be 
impossible to determine in every case the exact reason for the failure 
of the seed to germinate; and as some seeds of both strains did not 
germinate, it was not thought wise to attribute any of the failure directly 
to F. Uni , although it is quite likely that this organism was partly respon¬ 
sible. If there was any doubt as to the cause of the wilting of the seed¬ 
ling after it appeared above the ground, it was determined by isolation 
methods in the laboratory. After the number of plants was recorded 
they were kept under almost daily observation. Notes were taken 
every week where possible and the number of healthy, wilted, and dead 
plants recorded. Any plant which showed undoubted wilt symptoms 
was recorded as wilted. This method of note-taking made it possible 
to compare the rate of wilting of the hybrid plants with that of the 
susceptible strain. As time and space were very limited it was found 
to be undesirable to grow all plants to complete maturity. It was then 
necessary to select some stage in the development of the plant as the 
end point for observation and note-taking. At this stage all plants 
which were not to be kept for seed could be removed and other seed 
planted. The flowering stage was selected as being the most favorable 
to cease note-taking, for at this stage the plant has reached its maximum 
activity and very little noticeable infection takes place after this time. 
Part of the hybrid seed was grown in clean soil in a different green¬ 
house where there was no chance for infection by F. Uni . These plants 
were self-fertilized as previously described in order to obtain seed for 
the next generation. By this means seed was obtained from plants 
that might have been destroyed by wilt if they had been grown in 
infected soil. 
RESULTS OBTAINED FROM THE CROSSES 
The parent strains, as previously stated, were thoroughly tested on 
“flax-sick soil” before the crosses were made and were found to be 
uniformly resistant or susceptible, as the case might be. However, 
some of the plants of the resistant strain wilted in later experiments. 
Results obtained from the progeny of crosses show that there is a great 
difference in individuality among plants of any strain with respect to 
its resistance to wilt. This difference was shown very strongly in the 
two generations grown, the results being so widely different from indi¬ 
vidual crosses that it will be necessary to discuss the different crosses 
or groups of crosses separately. The first generation from certain 
crosses proved to be entirely, or almost entirely, resistant to wilt. Others 
were intermediate with respect to resistance, while still others were 
entirely susceptible. In cases where there was entire or partial sus¬ 
ceptibility a difference in the time and rate of infection was noticed 
as compared with the time and rate of infection of the common, suscepti¬ 
ble flax. In some experiments the common flax would be almost entirely 
