Abstract: Comparative anatomy of the stems of 10 species in Bryum from the headwaters of the Urumqi River was researched using the paraffin sections and scanning electron microscopy (SEM).The results showed that the stems of 10 species in Bryum were constituted of three parts,i.e.the epidermal,cortex and central axis.Epidermal cells were small,and the cell wall thickened strongly.Cortex cells arranged neatly or in a mosaic way,and the cell wall thinned gradually from outside to inside.Axis cells occupied small area,and the corner of cell wall thickened.Pores were distributed irregularly on the cell wall of stem,and the adjacent cell walls were thick with flaky or granular cuticle ornamentation on their surface.These characters would be the survival strategy of plants in severe environment for a long time,and they revealed that the stem of Bryum was characterized by the strong cold-resisting and drought-enduring capabilities.These species are quite similar in morphology,but each species has different anatomical structure,which can provide a taxonomical basis for species identification.

Key words: Bryum, plant stem, anatomy, SEM, Urumqi River