Discontinuous lines on the radial face of wavy-grained xylem as a manifestation of morphogenic waves in the cambium

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There appear in the wood of <em>Entandrophragma</em>, beside the basic interlocked grain, local minute undulations of grain the manifestation of which are checkered figures, either slanting or horizontal, on the radial face of boards. In reference to the model the slanting checkered figure is interpreted as the result of sudden appearance in the cambium of a wave of orientational tendency (morphogenetic wave) of relatively short wavelengths and stabilized amplitude from the moment of its appearance, moving vertically. This wave induces undulations in the arrangement of cambial initials. The undulation pattern also moves, however, its rate is half that of the morphogenic wave rate. The amplitude of the undulations oscillates between a maximal value and null which means that in successive wood layers there is wavy grain alternating with straight grain. The horizontal checkered figure may be explained by a local shift of the prase by one half of the period of the morphogenic wave of relatively long wavelengths underlying the interlocked grain formation.