The fiber processing characteristics of a cotton crop are determined by the maturity and variability of the individual fibers within the crop. Immature fibers are finer, flatter, and more elastic than fully mature fibers of a genotype because the fiber walls are thinner and the fibers are incompletely 'filled' with secondary wall cellulose. Consequently, immature fibers tend to stretch elastically, rather than break, when tension is applied and can recoil into tangled snarls when tension is released. The snarls and knots formed during fiber processing often contain entrapped mature fibers, and these tangled fiber masses appear in yarn and finished fabric as neps visible to the unaided eye. Further, the lower cellulosic content of the cell walls of immature fibers results in decreased dye uptake, which is seen as undesirable color shadings or barré when fibers of markedly different maturities are combined or in 'white' specks when the immature and mature fibers in a nep mass do not dye evenly and to the same degree.