Microscopic examination of cotton fibers in cuprammonium hydroxide solutions

During treatment of cotton with cuprammoniulIl hydroxide solutions, the cellulose dissolves, leaving residues which vary in amount and in structure, depending upon the degree of purification of the fib ers. The undissolved residue from raw and from dewaxed fibers consist s principally of fragmented shells that formed the outer surface of the fibers, and, to a lesser extent, of material from the lumen. Both of these residues are isotropic and stain deeply with ruthenium red. Fibers from which both wax and pectic s ubstance have been removed dissolve in cuprammonium reagent, leaving only a very small amount of isotropic residue which exhibits no definite cytological structure.