STUDIES OX PLAX RETTING. 
55 
flax stem. On tlie first stage of retting, we observe the destruction of the cam- 
bium layer, and then of parenchyma, accompanied with the separation of fiber 
bundles. As the retting proceeds, the isolation of the fiber itself and the 
detachment of cuticles take place. Nearly all of the constituents of stems are 
subjected to chemical changes which are induced by the combined action of 
micro-organisms and of extractive power of water. The loss of weight in the 
stem may therefore be taken as a measurement of retting grade. 
3. The anatomical and chemical changes take place not on all parts of 
stem but only on the bark portion i. e., outer layers of cambium. The xylem 
and pith remain almost unchanged. 
4. The essential matters which are lost during retting are pentosan, or 
gummy substance, in the bark portion and fiber (cutin, lignin and cellulose). 
Of the three ingredients composing pentosan-free fiber, the lignin remains al- 
most unchanged, cellulose loses its small quantity, accompanying the destruc- 
tion of surrounding tissues of fiber bundles in the bark portion and cutin is 
detached mechanically in the later stage of retting, with the destruction of 
other tissues. 
5. Among other ingredients, tannin is lost completely. The larger part 
of the mineral matters and of glucose are also lost. The quantity of protein 
and fat are very small and their loss may be neglected in consideration. 
6. The gummy substance, or pentosan, in the bark portion of the stem 
is made up largely of xylan and araban, with a small quantity of methyl 
pentosan. 
