FLAX-STEM ANATOMY IN RELATION TO RETTING. 13 
_ white color. This change in color is not dependable, as flax stems 
_ that are well cured may be practically white in color when first 
_ placed in the retting tank. The change in color is closely associated 
with the last stages in retting, although the eye may not be depended 
- on to decide between the different degrees of lightness in color. This 
_ change may be noted as a color change or as a disintegration process 
_in the exterior portion of the cortex. Figure 9 shows a gradual in- 
_ crease in lightness of color as the bacteria disintegrate the epidermis 
and the outer parenchyma. The stem on the left is distinctly cloudy 
and murky in color, owing to the loosened cell contents in the tissue 
_ between the cuticle and the fiber bundles, although the normal color 
_ of the unretted stem is light yellow-brown. In the center is shown 
a stem that is murky 
only in spots; the stem 
is light colored, and 
the cuticle is loosened 
excepting at these 
spots. On the right a 
stem is shown that is 
~ much lighter in color 
- and whose retting is 
very nearly completed ; 
the cloudy areas are 
very small, and the 
tissue between cuticle 
and fiber bundles ap- 
pears to have been de- 
stroyed excepting in 
those areas. The maxi- 
mum lightness in stem 
color is reached when 
the cuticle sloughs off. 
If the fibers are suffi- Fic. 8.—Water-retted Dutch fiber of good quality. Note 
ciently washed at this the fineness of the strands and compare with those in 
point the naked fibers 78°" %* 1° 
may be seen, glistening and transparent against the white back- 
_ ground of the wooden core. 
The leaf scars resisted the retting process of disintegration for a 
long time, and their disappearance was one of the last changes in 
the external appearance of the stem. Fiber bundles and the wooden 
core branch out into each leaf in the growing plant. When the 
leaves drop off at maturity the scars left by them are covered by a 
waterproof substance known as suberin that cements together the 
_ tip ends of the branches of the wooden core and fiber bundles that 
formerly fed each leaf. These areas are known as leaf scars and 
show up as dark-brown heart-shaped spots about 0.5 to 1 millimeter 
in diameter at intervals about every half inch or nearly every centi- 
meter along the stem. This means that in a stem 75 centimeters 
(30 inches) long there will be close to 100 leaf scars forming water- 
_ proof unions between the fiber bundles and the wooden core. The 
55159—23—_3 
