The mechanism of inflorescence abscission was investigated by microscopic observations on longitudinal sections of buds during bud-burst. Cuttings of Italia cultivar were used for this study. The results in­dicated that the abscission of clusters was associated with the forma­tion of the abscission layer. The zone was formed during the stage E of bud- burst according to Baggiolini. It was developed in the part of the first branching of the cluster, adjacent to the first bract. It was com­posed of 5-8 layers of cells. These cells were less regid and showed poorer cementing properties than those neighbouring cells. In rare cases, very little number of clusters were transformed into tendrils. They were only those clusters which were born already, having tendrils as the first branch.