4 BULLETIN 1185, U. S. DEPARTMENT OF AGRICULTURE. 
of the same variety 1.7 millimeters in diameter. The photograph 
here reproduced represents the average size, enlarged six times, of 
fiber bundles that may be found in stems of these respective diam- 
eters and shows how close the association is between fine stems and 
fine fiber. 
Measurements were made of the fiber bundles from stems of a 
selection in which the variations due to heredity have been eliminated 
and the variation in fiber size may be regarded as due almost en- 
tirely to the differences in stem diameter. The fiber bundles of 
this selection, Yale (10), a strain selected at Yale, Mich., in 1920, 
measured from 0.06 to 0.07 millimeter in stems 1.5 millimeters in 
diameter. The fiber bundles in stems 1.1 millimeters in diameter 
taken from the same selection were less than 0.04 millimeter in diam- 
eter. The term diameter in reference to fiber bundles means the 
width measured tangent to the circumference of the stem. 
The average number of fiber bundles is not materially less in a 
stem of small diameter, and the fiber bundles are necessarily smaller 
in the fine stems, as they are crowded together into a smaller girth of 
cortex. Since the opposite is also true, a thin stand of flax results 
in stems of large diameter that produce coarse fiber. For best results 
the stems should be 
uniform and should 
not be more than 1.4 
millimeters or much 
less than 1.2 milli- 
meters in diameter. 
It is only when large 
and small stems that 
fall outside of this 
range are included 
that there is much 
variation in the num- 
ber of fiber bundles 
Fic. 1.—Variation in the size of fiber bundles of flax due SAF 
to differences in the diameter of the stem. The fibers clue to the stem di 
on the left were taken from a Sed te eee es ameter variation. 
diameter, and the relatively coarse fibers on the rig # 
were taken from a stem 1.7 millimeters in diameter. — Part of the lack of 
uniformity in fiber 
fineness in Blue Blossom Dutch is probably due to the great variety 
of strains of flax that are present in this variety. Strains that vary 
in stem length and in fineness of fiber have been selected from this 
variety in Ireland? and in the United States.° The possibilities that 
are present along this line of selection for increased fiber fineness are 
indicated by a study of the fiber bundles in two closely related pure 
lines. The influence of heredity has given 36 fine fiber bundles to one 
pure line selected from Blue Blossom Dutch, while to stems of the 
same diameter of another pure line it has given only 24 relatively 
coarse fibers which are fully half as broad again as those of the 
former. 
It is not easy to untangle all the interrelating factors of environ- 
ment and heredity, but it has been shown that the quality of the 
Hunter, H. Improvement of the flax crop by propagation from selected plants. Jn 
Jour. Dept. Agr. and Tech. Instr, Ireland, v. 15, p. 245-246. 1915. 
Stewart, John W. The Irish flax-growing industry and how it may be improved, 
p. 126-129. Coleraine, Ireland. [1922?.] : 
5 Davis, Robert L. Op. cit., p. 19. 
