Abstract:The structure of secondary xylem of 6 species of Calligonum, grow in desert region of Gansu. China. was studied. There were wide and narrow two kinds of vessels, which were densely aggregated into clusters with a high molti-pore rate and short vessel elements of small average diameter. All species had exclusively simple perforation in oblique and horizontal end walls. Vessels had spiral thickenings and intervessel vestured pits, and inner aperture extended outwards forming many irregular bluges. Among them those of C. arborescens were the most outstanding and except C. klemertzii, the rest species had more or less tylosis in the 5-year-old stem. There were short libriform fibres. A portion of the fibres had glutinous substance composed of polysaccharides. Rays were low, homogeneous, and of multiseriate and uniseriate. Ray cells and axial parenchyma were riehed in glutinous substance. In addition, there were also interspecies differences in the amount of pit vesture, crystals, the presence or, absence of vessols with tylosis, ray height and quantity of the fibres with glutinous substance.