Abnormal Tissue in Swollen Stemwood of Chamaecyparis Obtusa Sieb. ' Zucco

Abnormal tissue which was laid down in the boundary between the annual rings in 1973 and 1974 in the swollen stem wood of Chamaecyparis obtusa Sieb. ' Zucco has been studied. The abnormal tissue was an aggregation of polyhederal-shaped thick-walled parenchyma cells containing dark-coloured deposits, and shaped like radially elongated spindles in transverse section. The axial length of these tissues was very high, measuring 50 to 80 mm longitudinally. The thin-walled tracheids adjacent to the abnormal tissue were collapsed in a region over 20 cells wide radially. The formation of the abnormal tissue containing the darkcoloured deposits, tracheids with additional wall layer and trabeculae, indicate the structure to be caused by injury. It is suggested that moisture stress induced the collapse of tracheids during secondary wall thickening, and thus forming radial fissures which are in turn filled with callus tissue arising from a proliferation of growth from the ray cells. The subsequent swelling appears to be a secondary effect caused by the proliferation of abnormal cells.