韧皮层由排列紧密的纤维细胞构成，它常年输送养分，使茎秆长高、长粗、长叶，也赋予茎秆强度及坚固性。
单中柱：原生中柱的一种类型，是由韧皮部、中柱鞘和内皮层包围着内方的木质部构成的实心中柱。
Haplostele a type of protostele having a solid strand of stele with the xylem on the inside encircled by phloem pericycle and endodermis.
在茎的次生结构中皮层与韧皮部之间有一层扁平形细胞；
There is a layer of compressed cells in the secondary structure of stem.
鸭跖草的木质部为六原型，韧皮部与木质部相同排列，根皮层中分布有粘液细胞和晶体细胞。
The phloems rage alternate with xylems. There are mucus cells and crystal cells in cortex of root. And vascular bundles scatter in stem.
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