Measurements of the reversing spiral in cotton hairs

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Abstract
The paper embodies selections from a mass of statistical data describing the dimensions and form of the spiral arrangements which occur in the cell wall of cotton hairs. The spirals may be dexter or sinister, and their reversals are apparently predetermined during growth in length. Genetic and environmental influences do not affect the statistical peculiarities of the reversals. The final adult length of the hair, and the time taken in reaching that length, do affect the reversal distribution. Nearly all the seed hairs of Gossypium begin to grow on a sinistral spiral. This basal sinistral spiral increases in length, is broken up, and later additions may be made to its fragments. Similar extension, fragmentation and subsequent addition take place with the later dextral spiral. The angle of the helix varies somewhat around 2 modal values, approximately 27 dexter and 27 sinister. The local variations of the angular value are quite unaffected by inversion of the "hand" of the angle from dexter to sinister. Dexter and sinister wall structures have been found in some hairs to have different structural properties in their resistance to collapse after the death of the cell. A tentative explanation of the causation of reversal is suggested; but attention is directed to its insufficiency and to the need for experimental evidence.

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