In nonwoody plants the primary xylem is the only water - conducting tissue , but in mature plants with secondary growth this function is mostly taken over by the secondary xylem 在尚未木质化的植物中，初生木质部是唯一的输水组织，但在具有次生生长的成熟植物中，该功能大多由次生木质部行使。
We have observed the following characteristics of anatomical structure and development : ( 1 ) the primary roots belong to archetype and the lateral roots occur in the position toward the xylem of the vascular cylinder ; ( 2 ) the root endodermis consists of thicken casparian strips , and there are from two lo four layers parenchyma cells near the pericycle ; ( 3 ) the pith and resins canals are absent in the toots ; ( 4 ) secondary structure occurs in the root hair zone , and vascular cambium is formed from the parenchyma cells between the primary xylem and primary phloem ; ( 5 ) tanning materials are abundant in pericycle cells and phelloderm cells ; ( 6 ) sclereids are found in secondary phloem , and rays are rather rich in secondary xylem 结果表明：气生不定根具有以下结构特征和发育特点： ( 1 )根为二原型，侧根正对着木质部发生； ( 2 )幼根内皮层细胞具凯氏带加厚，维管柱内紧挨中柱鞘内侧具有2 ~ 4层大型薄壁细胞； ( 2 )根中无髓和树脂道； ( 4 )次生结构发生于根毛区，维管形成层由初生木质部和初生韧皮部之间的薄壁细胞转化形成； ( 5 )中柱鞘和栓内层细胞富含单宁类物质； ( 6 )次生韧皮部有石细胞，次生木质部射线发达。
It was shown that vessel elements in secondary xylem of p . emblica have many different forms and most of them have tails and their perforation plates divide into two types : ( 1 ) there is one simple perforation plate at each end of the vessel elements and ( 2 ) there is one simple perforation plate at one end of the vessel elements and two simple perforation plate at the other end ; ( 3 ) a few vessel elements have special inclusions ; ( 4 ) the intervascular pits are alternate pits ; ( 5 ) the pits between the vessels and rays are mixed pits , pits with transverse gashes and scalariform pits 结果发现，余甘子次生木质部导管分子中存在着许多不同的样式，导管分子大多数具尾；其穿孔板存在着两种类型： ( 1 )两端均为1个单穿孔板； ( 2 )一端为1个单穿孔板;另一端为2个单穿孔板； ( 3 )极少数的导管分子具有特殊的内含物； ( 4 )管间纹孔式为互列纹孔式； ( 5 )导管射线间纹孔式为混合型纹孔与横列刻痕状纹孔以及梯状穿孔。
The secondary phloem parenchyma cells and secondary phloem ray parenchyma cells were the preferential sites for protein storage to the xylem parenchyma cells whereas a large amount of vegetative storage proteins was present in xylem , especially in the primary xylem and the inner secondary xylem of the extended stems 营养贮藏蛋白质优先在次生韧皮部的韧皮薄壁细胞和韧皮射线薄壁细胞中积累，在新梢伸长生长停止后，新梢基部茎的木质部中也积累了相当数量的营养贮藏蛋白质，主要分布在初生木质部和内侧次生木质部的各种生活的薄壁细胞中。
