Zur Anatomie und Physiologie der Zuwachszonen- und Jahresringbildung in den Tropen

Distinct zones of growth were usually only found in tropical deciduous trees with a periodically resting cambium. Reversedly a periodically resting cambium proved not to produce always distinct zones. All possible combinations of cambial activity and the formation of zones were shown to occur in the tropics. The zones could be distinguished in cross-sections by a) radial compression of the fibres formed before the new burst of cambial activity, b) a thin circular layer of parenchyma, c) a thin layer of libriform fibres, d) alternating widths of layers of libriform fibres and parenchyma, e) layers alternating in vessel diameter or arrangement. Most species formed either marked zones in east and west Java or less marked or irregular zones in the more even climate of west Java. Only a few species formed no growth zones at all in the more even climate.Young trees often did not form growth zones or only temporary ones, so that the zones were not a direct indication of age. Imported evergreen trees (except leafy trees with individually flushing branches) from cooler climates had no zones or vague ones. Renewed growth in leafy trees was always induced by substances or stimuli conducted from the sprouting leaf buds (and later from leaves) or from flowers (in leafless trees)