PEDIGKEED 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 North 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 dekd 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.^ 



These percentages have been called by Prof. Frank Spragg the 

 coefficient of yield.^ 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. 188-193. 



^ Spragg, Frank A. The coefficient of yield. In Journ. Amcr. Soc. Agron., v. 12, no. 5, 

 p. 168-174. 1920. 



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