At maturity, the almond pericarp dehisces along the ventral suture, a region that originates by fusion of epidermal cells and subsequently differentiates into a separation layer. We have characterized the ontogeny of the fusion–dehiscence zone with emphasis on cell wall characteristics by using cytochemical methods for detection of pectin, cutin, cellulose, and lignin to examine the middle lamellae and primary and secondary walls in dehiscence-zone cells. Carpel margins became united postgenitally along opposing epidermal layers giving rise to the suture. Fusion-zone cells host epidermal characteristics, elaborated broad pectinaceous walls, and ultimately formed a discrete band of cells that dehisced along the original line of fusion by dissolution of cell wall pectins. Treatment of treeborne fruits with 1 ppm ethylene gas or extraction of sectioned material with cell wall hydrolases resulted in cell wall changes similar to those in predehiscent fruits.