Cell events i n cambium, connected with the formation and existence of a whirled cell arrangement

The history of cambium development was reconstructed on the basis of serial tangential sections of a woody tumour of Picea excelsa (Lam.) Lk. On the area with whirled arragement of the tracheids intrusive growth was found to occur at the lateral radial and longitudinal edges apart from its normal occurrence at the radial apical edges. Intrusive .growth at the radial lateral edge leads to forking of the fusiform initial in the cambium plane. The growth which appears on longitudinal lateral edges oocurs between the tangential walls of cells in neighbouring storeys. In such places a drastic reconstruction of the cell arrangement in neighbouring annual rings was observed. Intrusive growth. between the tangential walls leads to a whirled arrangement of tracheids