Stains for the Primary Wall of the Cotton Fiber

Abstract

Several methods are described for distinguishing between the primary wall of the cotton fiber and other fiber components, such as the lumen and the secondary wall. The primary wall, a membrane less than 0.5 μ thick covering the entire fiber, has been stained while still attached to the fiber as well as after it has been mechanically stripped from the fiber. The stains include aqueous or alcoholic solutions of ruthenium red, methylene blue chloride, Nile blue sulfate, oil red, Sudan black B, iodine, and Simons' stain. Various concentrations of sodium hydroxide, cupri-ethylenediamine hydroxide, or sulfuric acid have been used to enhance color changes and to cause cellulosic swelling. Fibers that have been stained with Simons' stain and then swelled with dilute cupri-ethylenediamine hydroxide have shown the greatest color differences between the primary wall and the lumen.