FLAX-STEM ANATOMY IN RELATION TO RETTING. 93 
plunged into a glass cylinder of clear warm water, the external 
appearance may be observed readily. The stems should not be placed 
in water that is colder than the retting water if they are intended 
- for use in testing for completion of retting, as the fibers cling more 
- tenaciously to the stems when cold. Almost simultaneous with the 
positive leaf-scar test the cuticle will be noticed floating away from 
' the stems in pieces 3 to 5 centimeters long and several millimeters 
wide, and at any place where there happens to be a crooked bend in 
the flax stem the individual fiber bundles are to be seen drawn away 
_ from the wooden core. Also at this time the stems become light 
_ yellow to almost white in color, and the cloudy or murky appearance 
present at an earlier stage has been lost. The disappearance of the 
leaf scars, a slight swelling at the nodes around the leaf scars, a 
tendency of the fibers to pull away from the core, a lightening of 
@ 
Fic. 19.—Leaf-scar test for the completion of the retting process of flax fibers. Retting 
is incomplete. Note the fibers clinging at the leaf scar or node (n). The sizes of 
ae Mee stems in Figures 19 and 21 to 23 are exaggerated as compared with the size 
of the hands. 
the stem color, and the mechanical separation of the cuticle all 
appear to be associated with the positive leaf-scar test. 
_ fRtetting experiments have been conducted to determine whether 
_ the best quality of fiber may be obtained through the use of the leaf- 
_ scar test or whether the process should. be carried still farther and 
the epidermis test used to supplement the leaf-scar test. The epi- 
dermis test is made by breaking the wooden core and moving one 
portion of the stem about 3 inches to one side of the other portion, 
keeping at the same time the axes of the two portions parallel, and 
_ then swishing the cortex to and fro in clear water. If all the cuticle 
separates and floats away in pieces, showing that the epidermis is 
_ entirely destroyed, leaving the fibers of fine diameter and well sep- 
_ arated from the rest of the cortex, retting is complete. If, as in Fig- 
ure 21, the first step in the epidermis test shows the epidermis cling- 
ing in practically an undivided condition to the fibers, retting is 
incomplete. Figure 22 shows the first step in the epidermis test 
when the fibers are so well separated and retting is so nearly com- 
plete that it is necessary to carry the test still farther and swish 
