LINUM USITATISSIMUM 401 



striations in successive lamellae is alternately right- and left- 

 handed. 



Fiber Lignification. — Lignification is not necessarily uniform 

 in all the fibers in a given pericyclic area nor even in an individual 

 fiber, and one fiber of a group may be strongly lignified while 

 adjacent ones show little or no deposition of lignin. In general, 

 the peripheral fibers in a group tend to be more strongly lignified 

 than others; and it has been noted that this is also true of fibers 

 located immediately centrad to a lenticel. In regard to the rela- 

 tion of lignification to the position of the fiber in the stem, it has 

 been demonstrated that it is most extensive in the fibers at the base 

 of the stem, and increases as the stem matures. This fact is of great 

 importance in fiber flax because of its bearing on the process of ret- 

 ting and the final texture of the fibers. In instances where the flax 

 becomes too mature, retting, which involves the decomposition of 

 the middle lamella and the primary wall, is less complete and the 

 fiber is coarse and harsh in texture. 



Lignification is usually restricted to the middle lamella and 

 primary wall; and there is little, if any, lignin in the secondary 

 wall. This explains the fact that investigations, carried on to 

 determine the degree of lignification, show the presence of more 

 lignin in unretted fibers than in those which have been isolated by 

 retting. The middle lamella is the first region to become lignified 

 as the fiber matures, and lignification may stop at this point. In 

 some cases, however, it involves portions of the primary wall, and 

 may finally extend more or less completely through it. This 

 decreases the commercial value of the fiber, as it is less easily pre- 

 pared for market, and the fiber is of inferior quality, tending to be 

 harsh and brittle instead of exhibiting the desirable qualities of 

 smoothness, strength, and flexibility. 



The chemistry of lignification is not entirely clear; but it has 

 been suggested by Anderson (x) that it "is not a conversion of the 

 cellulose directly into a lignified wall, but that the cellulose first 

 undergoes a transformation to pectin-like substances." 



Vegetative Regeneration of the Plant. — As early as 1857, 

 Reichardt (18) observed certain phases of vegetative regeneration 

 in the shoots of flax, and these have been verified more recently 

 by Tammes (xi) in Holland. Beals (4), in describing the phenome- 

 non of regeneration in flax, states, "first the epidermis divides and 

 then the innermost row of those cells and the stimulated cells of 



