18 BULLETIN 1185, U. S. DEPARTMENT OF AGRICULTURE. 
culty may be entirely overcome, however, through the use of test 
cylinders placed at intervals in each tank. The test cylinders are 
packed loosely, so that the stems may be withdrawn one at a time 
without rubbing against each other. Test cylinders may be made of 
three thin boards nailed together so as to form a three-sided prism, 
with a half-inch crack along one edge to permit the free circulation 
of water and with a small triangular piece of wood nailed across 
one end for the bottom. Withdrawal of the stems from the test 
cylinder is facilitated 
by cutting off the pani- 
cles of the stems and 
placing them in the 
cylinder with the root 
ends up. A test eylin- 
der may also be made 
of a section of bamboo 
about 24 inches in di- 
ameter by knocking 
out the nodal parti- 
tions in a piece long 
enough to hold the 
stems and boring many 
holes about 1 centi- 
meter in diameter in 
the side for water cir- 
culation. 
In the loose-core test 
the wooden core is 
moved in the direction 
of the root end of the 
stem, and the cortex is 
held stationary. There 
are a number of other 
= 2 i ways in which the cor- 
® ery ae eee tex and the wooden 
Fic. 13.—Retting flax, showing the persistence of the core may be separated, 
leaf scars. Retting has disintegrated nearly all the , P ome 
tissues in the cortex except the fiber bundles and the and these are divided 
cp dermis that overlaps them and holds them together. into three oroups. In 
he leaf scar is partly disintegrated, exposing the OTP. 
‘bundle traces. Explanation: ) = Bundle traces, ¢ = group 1 are included 
se r is, 3st I 1 tates v3 sear, = = = f . 
eed Bs ber bundles, 7 = leaf scar, wu = unde two w ays of making 
the loose-core test, in 
which the total resistance to separation of cortex and core may be 
felt at once. In group 2 are included various ways of testing the 
dissolution of the leaf scars, and these tests are therefore called 
leaf-scar tests; in the leaf-scar tests the resistance to separation 
of cortex and core may be observed at each node, one at a time. In 
group 3 are included the epidermis tests, in which it is intended to 
show the fineness of division of the fibers and the extent of the disin- 
tegration of the epidermis as indicated by the quantity of cuticle 
that has separated from the stem. In testing the efficiency of these 
various methods a double objective may be kept in mind: (1) What 
test or combination of tests is the most dependable for deciding 
when to terminate the retting process, and (2) what test is easiest 
P ‘ 
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