16 
BULLETIN 1185, U. S. DEPARTMENT OF AGRICULTURE. 
may be of use in testing wet stems may be eliminated. These 
changes are (1) the fineness of the fiber, which includes the complete- 
4 ! d He (Wie : 
one ‘k Aapal 
ee a TAA 
Path Wy 
48 mall; j J i 
—~. Slog = 
a 
a 
Y, 
M Hd 
1 
' 
LNB 
D 
raat 
= 
= 
ee nO es EE So, So, 
role a x 
Re eS ee 
>> 
—————————— = A 
CO Se ee 
ene 
ap — Fj 7 r 
- = ——a 
— a Sp Bes wae S 
re 
enna, 
tr = 20cm. 
Fic. 11.—A piece of unretted flax cortex flattened 
out to show the exterior view. The structure 
of the epidermis (e) is obscured by the under- 
lying tissue. The bundle traces are not visible 
in the leaf scar (l). The fiber bundles (f) show 
as dark strips. u==Undeveloped bud. 
ness with which the cor- 
tex is separated into the 
fiber bundles and also the 
final separation of the 
fiber bundles, particularly 
the larger ones into sev- 
eral smaller units; (2) 
the disintegration of the ~ 
epidermis, which includes 
the digestion of the pectin 
in the inner cell walls 
and the mechanical sepa- 
ration of the cuticle; and 
(3) the disappearance of 
the leaf scars as an indi- 
cation that the water- 
proof unions of fiber and 
wood branches at the 
nodes are broken down. 
MECHANICAL METHODS 
OF TESTING WET FLAX 
STEMS FOR COMPLE- 
TION OF RETTING. 
The problem that arose 
at this point in the study 
was how to devise a test 
or combination of tests 
for completion of retting 
that would include two 
or if possible all three of 
the changes most closely 
associated with comple- 
tion of rettine, namely, 
the disappearance of the 
leaf scars, the fineness of 
fiber separation, and the 
disintegration of the epi- 
dermis. The various steps 
in the Belgian or loose- 
core test were analyzed in 
order to determine why 
it 1s undependable and 
whether any part of it 
might be of use. In mak- 
ing the loose-core test the 
stem is broken about one- 
fourth of its length above the. base end and the short piece dis- 
carded. 
The cortex or cone of retted fiber is then pushed back 
several centimeters from the broken end (fig. 14), so as to expose 
