PEDIGREED FIBER FLAX. 7 



was stronger and less likely to vary than either the basal portion 

 or the top ; so this portion was always used in making the strength 

 tests. The stem diameter was measured at a point in the middle of 

 the portion chosen for the test, and if several stems were of equai 

 breaking strength the one with the smallest stem diameter was con- 

 sidered the strongest. In order automatically to determine the 

 stems with the greatest strength per stem diameter, the prac- 

 tice of dividing the breaking strain by the diameter was adopted 

 in 1919. This gives the strength per millimeter of diameter. The 

 manner of making the strength tests is as follows: The stems are 

 water retted at a uniform temperature so as to loosen from the 

 wood of the stem the cortex in which the fibers are located. A 

 piece 15 centimeters long is- cut from the center of the stem chosen 

 for the test. The wood is broken along the middle 2 to 3 centi- 



PiG. 4. — Completion of a strength test. Good fiber is indicated by breaking at several 

 points and snapping away from the stem. 



meters of this piece by rolling a glass tube over the stem without 

 breaking the fibers. The pieces of wood are removed by working 

 the stem with the fingers, and nothing is left but the fibers and 

 those portions of the cortex which remain clinging to them. The 

 strength tester (Fig. 4) is a horizontal machine with two pairs of 

 jaws, between which the ends of the individual piece of stem are 

 fastened. One jaw is rigid and the other, which is movable, exerts 

 a pull on the fibers which is registered in kilos to the tenth place. 

 This figure is known as the breaking strain. 



Eecords for 1917 and 1918 show that the extent of basal branching 

 is an inherited character, and it has therefore served as an eliminator. 

 Seed-flax varieties have as a rule four or more basal branches, and the 

 unselected fiber flaxes have two to four. The quality of fiber is poor- 

 est in the White-Blossom Dutch variety, the fiber flax with the largest 



