Cytology of the Ray Cells in Sapwood and Heartwood

It is a generally admitted opinion that all living cells in the wood of a tree lose their vitality when the sapwood is transformed into heartwood (Büsgen/Münch 1927, p. 124; Chalk 1957). On the other hand metabolic processes have been reported in the "dead" core of trunks (Gaumann 1928) and living parenchyma cells were observed in heartwood (Good and Nelson 1951). According to Chattaway (1952) such findings are due to the existence of a band of intennediate wood between sapwood and heartwood, which, owing to its incipient coloration, is often erroneously attributed to the heartwood. Since transformation processes occur in this transition layer, it is concluded that the intermediate wood represents a zone of intensified metabolism. With the goal of checking these findings in European timbers, a cytological study of wood parenchyma in pine, larch, yew, fir, spruce, hornbeam, linden, locust, beech, and ash has been performed. The necessary wood samples have been provided by the Winterthur Municipal Forestry Department; we should like to express our gratitude for this co-operation.