APPENDIX 453 



The following brief summary gives a few of the more important characteristics 

 of each species of textile fiber to be studied. 



GROUP A. SEED HAIRS. 



Cot Ion. — Seed hairs of the cotton plant (Gossypium). Fibers are long, color- 

 less, twisted, flattened, ribbon-like cells with thickened edges. Most fibers have 

 a central air-filled canal (lumen), polarize strongly; display brilliant polarization 

 colors. Consists of almost pure cellulose. No " lignin " present. 



Mercerized Cotton. — (Cotton treated with caustic soda.) Differs fiom ordinary 

 cotton in being cylindrical, rarely flat and is usually free from twists. The cells 

 are more lustrous, more transparent, and show fewer markings or striations. 



Kapok. — Seed hairs of Eidendron (species) and Bombax (species). Fibers are 

 thin, lustrous, transparent (under microscope in water), smooth, usually showing 

 no markings or striations. Cells are almost uniform in diameter, tapering rather 

 abruptly to a point at one end. The bases of these hairs, where attached, are 

 swollen, bulbous, and the swollen portions are distinctly reticulated. Commercial 

 samples consist largely of broken, doubled over and irregularly bent hairs. Polariz- 

 ation very weak. 



GROUP B. BAST FIBERS. 



Linen. — Bast fibers from the stems of flax (Linum). Individual fibers are long 

 pointed cylindrical cells; colorless, fairly uniform in structure. Many possess 

 a central lumen usually as a narrow line which often appears to be double. Char- 

 acteristic slight swellings or nodes are to be found at fairly regular intervals, with 

 fine almost invisible cross-lines. Nodes, dislocations and cross-lines more pro- 

 nounced in woven fabrics than in raw flax, and are distinct in worn linen. Raw 

 flax contains both " lignin " and cellulose. Bleached linen contains substantially 

 no " lignin." Usually polarize strongly and show brilliant polarization colors. 



Hemp. — Bast fibers from hemp plants (Cannabis). Bundles of long blunt 

 cells, not pointed at the ends as in flax; many cells have forked ends. All show 

 large well-defined central lumens. Long cells usually striated; cross-lines more 

 prominent than in flax. Nodes absent, but dislocations frequent and well marked. 

 In cross-section fibers are irregularly oval, and lumen flattened and irregular. 

 Medium polarization, colors weak to strong. 



Jute. — Bast fibers from a number of species of Corchorus. Bundles of fibers 

 whose cells are much shorter than hemp and with tapering, somewhat more pointed 

 ends than hemp. Lumen almost central, large, well defined, and often interrupted, 

 of irregular diameter, varying from one-half or more the diameter of the cell to a 

 narrow black line. Cell walls with longitudinal striations but free from cross 

 striations. In cross-section the cells are polygonal, five or six sided, with large oval 

 lumen. Fibers which have been thoroughly freed from vascular tissue polarize 

 feebly. 



Ramie — China Grass. — These two terms are applied interchangeably in com- 

 merce to certain linen-like fabrics made from the bast fibers of a number of very 

 different plants. Usually these fabrics are somewhat coarser than linen but have 

 a higher luster or sheen. 



