There is a layer of compressed cells in the secondary structure of stem.
在茎的次生结构中皮层与韧皮部之间有一层扁平形细胞；
The primary structure of stem consists of epidermis, cortex and vascular cylinder too.
茎的解剖结构也由表皮、皮层和维管柱组成。
"If you have got a bunch of stem cells sitting in a test tube, that is a long way from being a beautifully, anatomically organised organ like a kidney, which is quite a complicated structure."
即使你试管里有一大堆干细胞，但你离拥有一个漂亮地，结构上像肾脏一样复杂的组织器官还很远。
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