6 BUULETIX 1092, U. S. DEPARTMENT OF AGRICULTURE. 



tliird generation, but they did not result in strains of value. This 

 negative result may perhaps be due to the fact that only a limited 

 number of crosses "^vere made. The crosses betvreen selections from 

 the Blue-Blossorn Dutch and TVhite-Blossom Dutch varieties resulted 

 in strains that were intermediate in resistance to flax wilt. The 

 flax under greenhouse conditions took four and one-half to five 

 months to mature and made an abnormal growth. Some of the 

 plants reached a height of 170 centimeters (54^ feet), so that it was 

 found necessary to support them on wires. 



It was fotmd impracticable to handle large numbers of selections 

 with the centgener method, because of the time consumed in planting 

 seeds one at a time, and flax selections after 1914 were sown in drOl 

 rows. Unifonnity of growth conditions similar to those of the cent- 

 gener method was secured in 1918 by thinning out the rows to one 

 plant to the inch. 



ELIMINATION OF POORER SELECTIONS. 



Very early in the work those selections that were most promising 

 were sown on a larger scale than the others, so that in 1914 enough 

 seed had been secured from the one then considered the best to sow 

 it at frequent intervals throughout the experimental plats. From 

 year to year additional selections were made, as in the year 1909. and 

 wherever one of them growing next to this standard selection has 

 been judged inferior it has been discarded. This standard selection 

 has been called the " check," as it acts as a check on the soil condi- 

 tions. The check serves the same purpose as a ruler placed alongside 

 a plant and is in one respect better than a ruler, for it measures the 

 soil conditions by growing tall where the soil is rich and short where 

 the soil is poor. 



As more and more of the selections were discarded, those retained 

 became more and more like each other, because all of them possessed 

 in some degree each of the desired characters. (See the selections 

 shown in Fig. 1.) Thus, it became necessary to study a larger niun- 

 ber of characters as a means of elimination of the poorer selections. 

 In addition to length of stem and stem weight, the following char- 

 acters were added : Strength of fiber per individual stem, the amount 

 of basal branching, the A^itality of seed, and resistance to disease. 

 The check selection has furnished a ready means of comparison be- 

 tween the different selections for all these characters. Data were 

 rapidly accumulated on the check, as it was sown in many duplicate 

 plats and measured extensively. 



Strength tests were begun in 1912. and during the years 1913 to 

 1917 hundreds of strength tests were made imder the direction of 

 Mr. Frank C. Miles. In this way many inferior selections were 

 eliminated. It was found that the middle portion of the stem 



