8 BULLETIN 1092, U. S. DEPAETMEXT OF AGRICULTURE. 



number of basal branches, and the selection work has always aimed to 

 reduce this branching habit. The manner of branching can best 

 be studied in open drill rows where the plants, thinned down to one 

 to the inch, are not crowded and can develop normally. In open drill 

 rows the check selection never develops more than two basal branches, 

 and with more than half of the plants it has none at all. Any selec- 

 tion having more than two basal branches was discarded. 



Seed vitality received more attention as the work progressed. In 

 addition to making germination tests and taking notes on the stand 

 secured in the field, a study was made of the number of seeds per boll 

 of all promising selections. The number of seeds per boll when 

 complete fertilization occurs is 10. This number is rarely approached 

 under field conditions. The data of 1919 and 1920 confirm the earlier 

 work. The average number of seeds per boll is an inherited character 

 directly associated with the vitality of the seed. For example, Selec- 

 tion 1923, with the best vitality of seed, has a high count of seeds per 

 boll, and Selection 1812. with poor vitality of seed, has a low count of 

 seeds per boll. Hence, all selections having a decidedly low count 

 of seeds per boll were eliminated unless the count for the check selec- 

 tion, grown in the same part of the field, also ran very low. 



In the years 1914 and 1915 marked differences in resistance to wilt 

 were noted in fiber-flax selections when a natural sur-^ival of the more 

 resistant selections took place. The check. Selection Xo. 5, was at this 

 time superior to most of the others in resistance to wilt. In 1919 the 

 selection plat at Croswell. Mich., was planted on soil where flax stems 

 had been previously spread. All selections from the TTliite-Blossom 

 Dutch variety were completely destroyed by flax wilt, and not 

 more than one-fourth of the plants among the selections from the 

 Blue-Blossom Dutch variety, the other commercial fiber flax, sur- 

 vived. The check selection, planted in every other row. was more 

 than 85 per cent resistant. Corroboration of the results was secured 

 in 1920 through the cooperation of the Office of Cereal Investigations 

 of the Bureau of Plant Industry. Plats were sown with seeds fur- 

 nished from the selection plats of fiber flax by Mr. J. C. Brinsmade, 

 jr.. at Mandan and by Mr. W. E. Brentzel at Fargo. X. Dak. In 

 Mandan the check. Selection Xo. 5, was over 80 per cent resistant to 

 wilt, while the Blue-Blossom, Dutch variety was 21 per cent and the 

 White-Blossom Dutch only 1 per cent resistant. At Fargo, Selec- 

 tion Xo. 5 compared favorably with the most resistant seed flaxes in 

 both resistance to wilt and seed yield. At both jDlaces the order of 

 resistance of the different fiber- flax selections was approximately the 

 same as that obtained in the selection plat in Michigan: those selec- 

 tions which were more resistant in Michigan were also the ones most 

 resistant in Xorth Dakota. This work makes it j^ossible to eliminate 



