Cotton fiber cellulose synthesis and cellulose content at various post anthesis maturity stages of boll' development were studied in sixteen cotton varieties of Gossypium arboreum and Gossypium hirsutum species, grown in the 2001 crop year in New Delhi, under identical agro-climatic conditions. Cellulose content was estimated using Updegraff's method. Field matured seed cotton was harvested at the end of the crop season and ginned fibers were subjected to physical testing in an AFIS-HVI facility. X-ray orientation parameters were computed from the normalized azimuthal diffracted X-ray intensity scans of (002) reflections. Simple correlations were worked out among various parameters measured. Cotton varieties were indeed observed to vary in their synthesized cellulose content and such differences are genetically inherent. Varieties of Gossypium arboreum synthesized less cellulose compared to the Gossypium hirsutum cultivars, although the rate of cellulose synthesis within each variety, regardless of species, was observed to be practically uniform at any five-day interval. The range of variation in cellulose content was observed to be more than 260%. Uniformity ratio, HVI tenacity and average leaf area were positively correlated with cellulose content. X-ray angles of 40% and 50% correlated significantly with a negative cellulose content, (thereby) indicating an increased orientation of cellulose crystallites to the fiber axis, with a greater amount of cellulose synthesized. (C) 2003 Wiley Periodicals, Inc.