每个维管束的韧皮部外面有数层厚壁细胞，增加叶柄的机械支持作用。
There are some sclerenchymatous cells outside the phloem of each vascular bundle to increase the supporting force of the petiole.
以生物制片和光学显微技术研究了尼泊尔马桑根瘤维管束的形态结构和发育特点。
Morphological structure and the development of nodular vascular bundles of Coriaria nepalensis Wall. were studied by microscopical techniques.
而油细胞的颜色，非腺毛、叶迹维管束及维管束的多少则是显微上的主要区别点。
The color of Oil cell, the number of non-glandular hair, leaf-trace bundle and vascular bundle are distinct in micro-character.
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