Objective:To study the microscopic characteristics of Uncaria medicinal material from six different species

and provide basis for fundamental identification of Uncaria medicinal material. Method:Transection characteristics and powder microscopic characteristics of stem

hook and leaf from 6 species of Uncaria were observed under electron microscope. Result:The tissues and structures of different species of Uncaria were basically the same composed of epidermis

cortex

phloem

xylem and medulla from outside to inside. Most of the cortex

phloem and pith parenchyma cells of Uncaria contained brown inclusion

but there were different features in different species

such as the shape of main veins on the back of abdomen

the number of columns of the palisade tissue

the number of vascular bundles

and the type of crystal of calcium oxalate visible in parenchyma cells. The comparative microscopic characteristics of six species of Uncaria medicinal material showed that characters such as the transverse section profile of stem

the presence or absence of epidermal hair

the proportion of phloem and xylem

the presence of clear ring in cambium

the width of radiation ray

the scattered or radially connected catheters

the proportion of pith as well as the protruding shape of main veins (of leaves) in ventral and dorsal surface

the column number of palisade tissue

the type of crystals in parenchyma cells and the shape of hook

were used as the fundamental identification characteristics among various species. Powder identification included the shape of epidermal cells and the presence of oil droplets

ladder vessel and reticulate vessel within those cells. Conclusion:The above characteristics can be used as the identification basis for the six species of Uncaria medicinal material.