Readjustments of cambial initials in Wisteria floribunda (Willd.) DC. for development of storeyed structure.

•  This study has elucidated the mechanism of development of the storeyed cambial structure of Wisteria floribunda, a species characterised by very quick and early establishment of storeyed structure from a nonstoreyed procambium in close vicinity of the pith. •  Rearrangement of the cambial cells was studied in serial tangential longitudinal sections of axial wood parenchyma. •  The mechanism of cell rearrangement was found to involve not only the occurrence of anticlinal cell divisions, but also a concomitant intrusive growth of the ends of cambial cells of one cell packet along the tangential walls of cells of the neighbouring packet. During the process, the fusiform initials changed their position along the stem axis and became arranged in regular storeys. New positions of cells were thus achieved through first the vertical intrusion of cell ends between the tangential walls of neighbouring cells, and second the unequal periclinal cell divisions. •  The concept that radial longitudinal divisions of the fusiform initials are the main cause of the formation of storeyed structure of the cambium has been critically examined.