Fiber elongation ceases by about 24–28 days postanthesis, and by 50–70 days postanthesis fibers are mature and exhibit a thickened secondary wall and spiral twisting. Areas of contrast (spots) observed through the scanning electron microscope are speculated to be organelles “seen through” the relatively amorphous fiber wall, which lacks extensive fibrillar orientation of cellulose.
Fiber initials (epidermal cells of the ovule) begin their elongation phase on the morning of anthesis and are bounded by a thin primary wall. Stomata are abundant, particularly at the chalazal ends of ovules. Fertilization is accomplished, for most ovules, by the end of the first day postanthesis. Multipored pollen grains germinate in about ½ hr after deposition on the stigmatic hairs. Flower opening occurs at about daylight, although light is not required. The maximum rate of increase in floral bud length occurs during the 24 hrs preceding anthesis. In about 85 % of the flowers the basal, abaxial surface of two of the three bracts contains an outer involucral nectary occasionally, none, one, or three nectaries are found. Floral parts are morphologically well defined by two weeks preanthesis.
The first floral bud occurs on the 7–9th node approximately 35–40 days postemergence 20–25 additional days elapse until anthesis. This report assembles and pictorially presents observations on the timing of relatively uniform and well-defined developmental events in the cotton flower and its component parts.
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