GOSSYPIUM 



447 



different. In fibers grown under continuous artificial light there 

 are no lamellations, such as appear in fibers grown under field con- 

 ditions and then swollen in cuprammonia and subjected to pressure. 

 (Fig. 3.) On the other hand, continuous illumination has no 

 effect upon the conspicuous lamellations of the collenchymatous 

 cells . Although the light effect 

 may be correlated with the tem- 

 perature relations determined 

 by Kerr, it is suggested that 

 light may have an effect inde- 

 pendent of temperature. The 

 fibers grown under continuous 

 illumination have the same 

 convolutions and reversals as 

 those grown in the field, and 

 the spirally wound strands of 

 cellulose exhibit the same struc- 

 tural pattern. Limited tests 

 also indicate that the tensile 

 strength of the unlamellated 

 fibers grown under continuous 

 illumination is not significantly 

 different from that of lamel- 

 lated ones grown in the field. 



The structure of the fiber has 

 been represented diagrammati- 

 cally by Anderson and Kerr (i); 

 and they have described it as 

 follows: (Fig. ii8.) 



Fig. 118. Diagram of mature cotton fiber. 

 The apparently structureless primary wall of 

 cellulose and pectic substances is shown at base. 

 The next layer represents the cellulose structure 

 of primary wall with its three systems of cel- 

 lulose threads. Zone 3 shows first layer of 

 secondary wall at point of a reversal. Zones 

 4 and 5 represent second and third layers of 

 secondary wall. The growth rings formed by 

 the alternation of zones of dense with zones 

 of less dense cellulose are shown at top of fig- 

 ure. (After Anderson and Kerr, Ind. and Eng. 

 Chem?) 



"i. A primary wall contain- 

 ing cellulose and pectic sub- 

 stances. The cellulose micelles 



in this wall are grouped into delicate anastomosing threads which have 

 at least two systems of orientation: {a) a flat right-hand spiral, (Jj) a 

 flat left-hand spiral, and probably also (c) a transverse position. All 

 three systems seem uniform over the entire surface of the fiber cell. 



"i. A secondary wall composed of many lamellae of cellulose. 

 The lamellae are not separated from one another by non-cellulosic 

 substances but represent dense and less dense areas of cellulose. The 

 layers are formed of systems of spirally wound branching threads, and 

 the direction of the spiral is reversed at frequent intervals. 



