栓内层

生长龄不同，额外形成层、栓内层的宽度和细胞大小不同。

Roots are different in the width of supernumerary cambium and phelloderm and the cell .

结果：根横切面上栓内层的石细胞环带和次生木质部导管的排列方式、初生木质部为四原型等为显微鉴别特征；

Results : The circular belt of sclereids in the phelloderm , secondary xylem vessel order of the transverse section , and tetrarch of the primary xylem were microscopic characters .

另外，光皮型杜仲在栓内层分布有较少的，质地紧密的石细胞群；

Secondly , there was a little of collenchyma whose texture was tight in smooth type 's endothecium of phellem ;

但在以后的发育过程中，木栓形成层产生了多层栓内层薄壁细胞，维管形成层则产生了大量高度薄壁组织化的次生维管组织，从而形成了肉质膨大的块根。

The main cause of root tuber expanding is that phellogen produces many layers of phelloderm parenchyma cells and vascular cambium produces a lot of secondary vascular tissue that consists of parenchyma .

根系由不定根组成，根的初生结构木质部为2～4原型，次生结构中栓内层较厚。

Its root system is composed of adventitious roots . The primary xylem of root is 2 ~ 4 arches , and the secondary structure of root is characterized by a thicker phelloderm .

结果表明，绞股蓝人参皂甙主要分布在营养器官的同化组织及韧皮部薄壁细胞中，厚角组织、表皮及周皮的栓内层也有少量分布，木质部和髓薄壁组织中无皂甙分布；

The results showed that ginsenosides distributed mainly in the assimilating tissue and phloem parenchyma cells , very little in collenchyma , epidermis and phelloderm , and no coloration in xylem and pith parenchyma .