Washington, D. C. Octcber, 1923 
FLAX-STEM ANATOMY IN RELATION TO RETTING. 
By Rosert L. Davis, Assistant Plant Breeder, Office of Fiber Investigations, 
Bureau of Plant Industry. 
CONTENTS. 
Page 
TINTS 0 2) 6c i ee = = Ee See aes Wicks Bnet il 
The retting objective and some factors that may feiertene: Be deh are 2 ee vig ngey ies 2 
The progress of retting in the different tissues of the stem_ Hx nen 5 
Some macroscopic and externa] changes in the flax stem during Rettig: Sas 1 
Mechanical methods of testing wet flax stems for completion of retting__________ 16 
SUN Ws oe ea Stas eas ors Steep. at): Weameee Reh gre ey dl 26 
INTRODUCTION. 
The flax stem consists of two main parts, the central wooden core, 
hned with pith, and the cortex or bark, which completely encircles 
the wooden core. Between the wooden core and the bark hes the 
cambium layer, commonly known as the green inner bark. The fiber 
bundles are located in the cortex. The process of retting has the 
double object of separating the cortex from the wooden core and 
the fiber bundles from the nonfibrous portions of the cortex. 
Numerous efforts to ret flax by chemical methods have thus far 
failed to be sufficiently successful to supersede the natural methods 
of dew retting and water retting. In dew retting the stems are 
spread out on a meadow for four to six weeks, and irregular 
weather conditions may result in a very uneven product. In water 
retting the flax stems are submerged in water, and retting is accom- 
plished by the activity of bacteria, which dissolve the gums that 
hold the fibers to the surrounding tissues. Water retting may be 
controlled more satisfactorily than dew retting, 1s a more rapid 
process, and usually results in a more uniform product than dew 
retting. The scope of this bulletin is confined to water retting. 
One of the chief difficulties experienced in water retting is that 
of deciding when to discontinue the process. If the stems are re- 
moved before the critical point is reached the fiber will not be well 
separated from the cortex and will be both coarse and harsh. If the 
process is carried beyond the critical point of complete retting the 
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