Xylogenèse chez les Dicotylédones arborescentes. I. Modalités de la remise en activité du cambium et de la xylogenèse chez les Hêtres et les Chênes âgés

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Abstract
The pattern of cambial reactivation and xylogenesis has been studied in trees at least 30 years old. In the oak, a ring-porous tree, the cambium becomes active simultaneously throughout the bole; at the same time cambial reactivation, coming from swelling buds, proceeds from the upper part of the branches down the twigs. In the beech, a diffuse-porous tree, cambial reactivation first proceeds downwards at the rate of 5 to 10 cm a day in the branches; later, cambial reactivation occurs simultaneously throughout the bole. This simultaneous reactivation of the cambium in the whole trunk of the beech is independent of events occurring in the branches; the cambium may produce earlywood members in the trunk, whereas it may be resting in the lower part of the branches. Thus, there is no fundamental difference in the pattern of cambial reactivation between those two species, since the two sorts of cambial reactivation (the basipetal and the simultaneous reactivation) coexist in both aged beeches and oaks.