A 1919 research paper by W. Lawrence Balls reporting that the cell wall of cotton seed-hairs (lint and fuzz) is built of concentric layers, each representing one day's growth. Swelling the hairs with carbon disulphide and sodium hydroxide makes the layers visible, and counts on Egyptian cotton fruits of known age (9 to 50 days) match the expected 25 rings in mature lint. The paper covers the method, microscope setup, counts for each stage, an anomalous hair with a double wall, and conclusions. Line drawings and micrographs on plates 14-16 illustrate the rings.

A 1922 research note by W. Lawrence Balls and H. A. Hancock on the microscopic structure of the cotton hair cell wall. It describes the cuticle, primary wall, and secondary wall, and reports a spiral fibrillar structure (pit spirals) running through the growth rings. It relates this structure to the external convolutions of the hair, using dated boll samples, swelling and pressure techniques, and convolution maps. The note ends with eight numbered conclusions and a plate of nine micrographs of Sakel cotton hairs.