PEDIGREED FIBER FLAX. 9 
all except a very few selections which show promise of wilt resistance. 
The fact worthy of special note is that wilt resistance is not peculiar 
to a restricted locality, since fiber-flax selections proved to be resistant 
in Xorth Dakota as well as in Michigan. 
By the year 1918 the work of elimination had brought the number 
of selections still being considered down to 25 or 30. all of which 
were tall. It was not easy to distinguish between them, and it be- 
came necessary to use the check system more rigidly than before. 
The check rows were sown closer together, so that not more than 
two varieties were grown between them. The distance between the 
checks was about one-twentieth the length of the row. because if 
farther apart the soil variation may be too great for the check to 
indicate accurately whether the soil between it and the next check is 
good or poor. The rows were increased in length from 1 to 10 rods 
each, because a larger plat gives more accurate results. The plants 
were thinned to one to the inch, in order that there might be the 
same number of plants in each row and each selection might have 
the same chance to develop. Duplicate sowings in different parts 
of the field were made of each selection. 
Since only two varieties or selections were planted between checks, 
each one of them had the best selection or check growing beside 
it. This made it possible for notes to be taken at sight in com- ' 
paring them for resistance to disease, uniformity of growth, and 
resistance to lodging. If a selection had more dead straws than 
the adjacent check row. it was considered inferior to it in disease 
resistance. If it lodged or bent over from rain or heavy dew more 
than the check row. it was marked as not resistant to lodging. If 
the stand was very irregular and the stand of the check growing 
alongside was all right, it was graded as having a low vitality. 
COMPARING WITH THE CHECK BY PERCENTAGES. 
For more accurate comparison of stem weights, seed weights, 
stem lengths, number of seeds per plant, and other measurable 
characters, these data have been reduced to percentages, a method 
adopted in the plant-breeding work in Scandinavia. 1 
These percentages have been called by Prof. Frank Spragg the 
coefficient of yield. 2 If we have Selection A. which yields three- 
fourths as much straw as the average of the check rows on each side, 
it is given a value of 75 per cent. If the weight of the straw of Selec- 
tion B is nine-tenths that of the adjacent checks, it is given a value 
1 Newman, L. H. Plant Breeding in Scandinavia, 193 p.. 63 fig. Ottawa. Ont.. 1912. 
Literature cited, p. 1SS-193. 
2 Spragg. Frank A. The coefficient of yield. In Journ. Amor. Soc. Agron., v. 12, no. 5. 
p. 168-174. 1920. 
107389°— 22 2 
