次生木质部由孔纹导管、 薄壁组织及射线所组成。
Secondary xylem consists of pitted vessels, parenchyma fibers and rays.
初生木质部与初生韧皮部之间可见到2—3层排列规则或不规则的薄壁组织细胞，但是没有维管形成层的发生。
Between primary xylem and primary phloem there are 2-3 layers of parenchymatous cells, regularly or irregularly arranged, but no cambial zone can be recognized.
伸向子叶的子叶迹，直接由原生木质部极外面的一群薄壁组织细胞分化形成。
The extending cotyledon traces differentiate directly from the parenchymatous cells which locate on the outside of the poles of primary xylem.
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