590 
Journal of Agricultural Research 
Vol. XI, No. u 
t 
tion to a greater extent, and for this reason it was more desirable to 
remove them as soon as possible after the seed began to set. 
For selfing plants the paper bags were used very little. The whole 
plant was covered with cloth. The most satisfactory method was to 
use wire cylinders about 3 inches in diameter and about 12 inches long, 
made of screening and covered with slips of finely woven white cloth made 
to fit. These cloth slips should be considerably longer than the cylinders, 
so that they can be tied at both ends. A piece of stout wire is pushed 
into the ground beside the plant, so that it extends a few inches above 
the top of the plant. The cylinder is then placed over the wire and the 
plant, and the cloth is brought together at the upper end and tied tightly 
around the large wire above the top of the plant. The lower end of the 
cloth is then tied around the wire and the plant above ground. The 
fruiting part of the plant is thus protected within the cylinder, where it 
produces seed in a fairly normal manner. These cylinders should be 
removed as soon as the flowering period is over and the fruit has set. 
methods used in growing the progeny from crosses 
Plants of the first and second generations which were to be tested for 
resistance were grown in flats and on benches of North Dakota “flax- 
sick soil” and Madison soil which was inoculated as previously stated. 
These experiments were conducted in the greenhouse throughout the 
year. There is a slight variation in temperature in the greenhouse 
with change of seasons, a condition that can not be prevented. It was 
shown by temperature studies (23) that a difference of a few degrees might 
greatly influence the rate and amount of attack of flax by F. Uni . By 
comparing the controls grown in winter and summer this difference will 
be observable. The high summer temperatures increased the severity of 
the wilt, even a few plants of the resistant strain wilting. 
The soil was well pulverized and the seed planted about 1 inch apart 
in rows about 4 inches apart. This made it possible to grow a large 
number of plants in a comparatively small area. In every case rows of 
both parent strains were planted in every flat or bench in sufficient 
numbers to serve as controls, and in some experiments selfed seed from 
the parent plants of the crossed seed wore planted as controls. The 
number of seeds planted was recorded in order to ascertain the percentage 
of germination. In the summer, when the greenhouse temperature 
ran high, the percentage of germination was low. In some cases practi¬ 
cally none of the seeds germinated. This perhaps was not due to tem¬ 
perature alone but to the increased activity of other physical and 
biological agents in the soil. As soon as the seed germinated and the 
seedlings appeared above the ground, they were counted and recorded 
as plants. Any plant that made its appearance above the ground was 
counted, even though it died in this stage from wilt. The results are 
