Sequential changes occurring in cell walls during expansion, secondarywall (SW) deposition and lignification have been studied in the differ-entiating xylem elements of Holoptelea integrifolia using transmissionelectron microscopy. The PATAg staining revealed that loosening of thecell wall starts at the cell corner middle lamella (CCmL) and spreads to ra-dial and tangential walls in the zone of cell expansion (EZ). Lignificationstarted at the CCML region between vessels and associated parenchymaduring the final stages of S₂ layer formation. The S₂ layer in the vesselappeared as two sublayers,an inner one and outer one.The contact raycells showed SW deposition soon after axial paratracheal parenchyma hadcompleted it, whereas noncontact ray cells underwent SW deposition andlignification following apotracheal parenchyma cells. The paratrachealand apotracheal parenchyma cells differed noticeably in terms of propor-tion of SW layers and lignin distribution pattern. Fibres were found tobe the last xylem elements to complete SW deposition and lignificationwith differential polymerization of cell wall polysaccharides. It appearsthat the SW deposition started much earlier in the middle region of thefibres while their tips were still undergoing elongation. In homogeneouslignin distribution was noticed in the CCML region of fibres.