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FLAX-STEM ANATOMY IN RELATION TO RETTING. 0 
fiber may be influenced indirectly by frost resistance. The coarse 
fiber produced by White Blossom Dutch is in part due to its marked 
susceptibility to frost, as its stand may be depleted by frost and 
coarse stems developed when varieties such as Blue Blossom Dutch 
and Saginaw escape with little injury.® ; 
It has been shown that straw quality may influence the retting 
product in strength and fineness of fiber and that the hereditary 
quality of the seed as well as the soil, climate, and season all share 
in exerting this influence. Therefore the objective of retting, that 
of producing fiber of the best quality, can not be attained unless 
pains be taken to assure uniform straw quality, It is important 
that the stems be fine and of uniform diameter. If possible a strain 
of flax selected for strength and fineness of fiber should be used, so 
as to eliminate the variation that may occur even in stems of the 
same diameter. These precautions will eliminate most of the vari- 
ables that affect retting and are due to straw quality, so that the 
variations that arise may be controlled through management of 
the retting process. 
FACTORS OF THE RETTING PROCESS AFFECTING THE QUALITY OF THE FIBER. 
‘The variables in the retting process itself are the nature of the 
retting bacteria, the temperature of the water, the rate of water 
circulation, the water quality (whether hard or soft), and the dura- 
tion of the ret. Of these factors the one that causes most trouble is 
the duration of the ret, or making the decision as to when retting is 
completed. A study of the process of disintegration of the flax stem 
as retting proceeded was undertaken in order to find out what 
changes in the flax stems were closely associated with the comple- 
tion of retting. 
THE PROGRESS OF RETTING IN THE DIFFERENT TISSUES OF 
THE STEM. 
The rapidity and order with which the different tissues in the 
flax stem are retted depends on the digestibility or solubility of the 
cementing substances that bind the tissues together, their accessi- 
bility, and the relative amounts of them present in the different tis- 
sues. The tissues of the flax stem that lie in the cortex may be 
divided into the fiber bundles, the phloem parenchyma lying be- 
tween the fiber bundles and the cambium layer, the parenchyma 
lying between the fiber bundles themselves, the epidermis that in- 
closes the stem, and the outer parenchyma that les between the 
epidermis and the fiber bundles. (Fig. 2.) 
Retting takes place first in the cambium layer (tissue 1, in fig. 2) 
where the pectin is quite soluble and where because of the very thin 
cell walls the layers of pectin or cementing substance are corre- 
spondingly thin. When flax stems are sterilized in water at 115° C. 
much of the pectin in the cambium layer is dissolved, and the cortex 
is so well loosened from the wooden core that the loose-core test is 
of no value at all as a positive indicator that retting is completed. 
The pectin in the tissues of the cortex is less soluble than that in the 
® Davis, Robert L. Frost resistance in flax. U. S. Dept. Agr., Dept. Cire. 264, 8 p., 
5 fig. 1923. 
