On the Anatomy of the Woody Stem of the Twisted Hazel, Corylus avellana L. ‘Contorta’

Data are presented concerning the internal structure of the woody stem of Corylus avellana L. ’Contorta’ the twisted Hazel. In the primary state the pericycle is noteworthy because of its poor development, which is in striking contrast to the situation in the normal Hazel. Because the primary shoot is twisted from the very beginning, the cambial cylinder is also twisted. In the loops, unequal amounts of secondary xylem are formed, with a larger quantity at the inner bends than at the outer bends. The changes in the cambial areas—decrease at the inner and increase at the outer bends—are almost completely parallel to the changes observed in the dimensions of wood vessel elements—decrease in length from the pith towards the inner bends of twisted parts of branches and increase in length towards the outer bends. In the majority of cases tension wood proved to be present at the outer bends. A method for localizing tension wood using fluorochromes is described.