The formation of periderm is relatively late and cork cambium is come from the cortex cells which arenear endodermis.

周皮发生较迟，其木栓形成层由紧靠内皮层的皮层细胞产生。

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Periderm cork cells was nearly square or irregular, large caliber, large quantities, cascading arrangement. The caliber of the outermost layer of cork cells was large, filled the air.

周皮中的木栓细胞为近方形或不规则型，口径较大，数量多，且层叠排列，最外层的木栓细胞口径大，充满了空气。

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