A method is described for isolating the lumen contents of the cotton fiber by digestion of the cellulose in chilled 72% sulfuric acid. Microscopical observations on the isolated "lumens" as well as the lumen in the whole fiber are reported. The isolated lumens appeared tubular in shape, and electron micrographs of thin sheets of the membrane material showed an unoriented, granular structure. The lumen residue isolated by sulfuric acid was found to be completely hydrolyzed by 1% sodium hydroxide, but only partly hydrolyzed in dilute mineral acid. Amino acid determination by paper chromatography disclosed no free amino acids in the lumen material; but in an acid- hydrolyzed sample, glutamic and aspartic acids, valine, alanine, and probably serine and arginine were found, in addition to several unidentified amino acids.

Effects of acetylation on the morphology and submicroscopic structu e of cotton have been studied by light and electron microscopy. The cross-sectional area of partially acetylated (PA) fibers increases with degree of substitution. The average refractive index of PA cotton decreases with increase in acetyl content, as do the indices measured parallel and perpendicular to the fiber axis. Refractive index measurement appears to be a feasible method for estimating the chemical composition of PA cotton. At early stages of esterification, unevenness of reaction along the length of fibers may be demon strated by dyeing and swelling techniques. Acetylation causes the surface of cotton to become smoother, and obliterates the micro- fibrillate pattern characteristic of scoured fibers. PA cotton fibers swell when embedded in methacrylic esters by polymerization. The swelling causes separation of the lamellae of the secondary wall, and permits electron microscopical observations on the interior elements of the fiber to be made on thin cross sections of the specimen. Fragments of PA cotton obtained by wet- beating show progressive loss of the fibrillate character of unacetylated cellulose as the acetyl content increases. At high degrees of substitution, the PA cotton fragments resemble the spongy particles obtained from wet- beaten acetate rayon and Arnel. The results of microscopical examination are considered in terms of fiber structure.

Changes in the cross-sectional area and circularity of cotton fibers tensioned in water and other media have been measured microscopically. It was found that the area increased significantly over that brought about by water-swelling alone. Fibers tensioned in bundle form at 0.45 g./grex for 1 hr. in water showed an average increase of 98% in area compared to dry untensioned fibers, and an increase in circularity (axis ratio) of 57%. These increases were not retained on drying, even when tension on the fibers was maintained. Immersion without tension in urea solution, ethylamine, or sodium hydroxide of mercerizing strength, followed by removal of the reagent and drying, in each case produced increases in area and circularity over those of the untreated fibers. Tensioning at 0.45 g./grex during im mersion in these reagents increased the circularity, but decreased the area with respect to the untensioned fibers. The elongation of fiber bundles tensioned in the various media was measured. The sodium hydroxide solution produced the greatest elongation.

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