STUDIES ON FLAX RETTING. 



37 



tion of the fiber but also the destruction of the cuticle took place. The 

 following are the chief results of our microscopical observations upon the 

 changes of the stem during retting. 



1. The cuticle strongly resists the action of micro-organisms and 

 other physical conditions, since we observe that, at the end of the middle 

 period and in the last period, it is gradually separated with the dissolution of 

 the other cell-walls. 



2. The outer walls of the epidermal cells are less destructible than the 

 inner. The inner walls begin to dissolve and allow their contents to exude, at 

 the end of the first period ; in the middle of the last period they were destroy- 

 ed completely with the other parenchyma walls. 



3. The cortical parenchyma walls are dissolved almost completely, in 

 the middle of the last period, after the destruction of the cambium layer. 



4. The dissolution of the internal cells of the fiber-bundles takes place 

 at the same time as that of the cortical parenchyma, but the isolation of the 

 fiber itself is observed at the middle or the end of the last period. 



5. The separation of the cambium layer occurs at the end of the middle 

 period. It begins to separate from the xylem portion and dissolves gradually' 

 so that the separation ,.f fiber- bundles from the; woody portion was found to 

 reach completion at the beginning of the last period. 



6. The changes of the xylem portion could not be observed even at the 

 end of the last period. 



From the above obervations, we conclude that the separation of the cam- 

 bium layer from the xylem portion takes place first and then follows the des- 

 truction of the cortical parenchyma and some parts of the epidermis ; the 

 isolation of the fiber itself and of the cuticle comes then in order. 



3. Wicrochemical Observations. 

 A. Reagents and Coloring Matters. 



1. Zinc chloride iodin solution. 20 parts of zinc chloride, 6.5 parts 



