Abstract: As a xerophyte, Crossidium crassinerve (De Not.) Jur. is newly reported in Shaanxi Province based on the specimens collected from Shenmu County. The genus is recorded in Shaanxi Province for the first time. Its morphologic and anatomical characters are described and illustrated. Some important structures, such as cell of chlorophyllose filament on costae, peristome, basal membrane, spore, antheridium and relationship between rhizoid and sand fixation, are observed under a scanning electron microscopy. The species is one of the typical xerophytes growing in arid and semiarid areas. Moss forms gradually the following morphologic and anatomical features to adapt the extremely arid environment: plants dwarf and are in dense turfs or small cushions, have dense and branched rhizoids; stems have central strand and leaf costa with guide cells; stem leaves imbricate and are concave in distal half; upper part of the leaf margin is strongly recurved; costa excurrent is just like a long hyaline hair; filaments restrict the adaxial surface of costa; the species not only produces the sexual structure sporophyte, but also generates a lot of asexual structure gemmae in this area. The species is mainly distributed in desert, semiarid desert or hilly regions covered by sand sheet in the regions between 15°-50° N in the world. It plays the important ecological roles in sand fixation, water storage and vegetation succession. It is restricted in Inner Mongolia and Xinjiang of northwest China. The new record provides a reference for the flora in Shaanxi and even in China.

Key words: moss, Crossidium crassinerve, ecological role, new record, Shaanxi Province