Abstract: It is always difficult to classify the Brachytheciaceae plant species. In this study, the microstructures of leaves of 10 Brachytheciaceae plant species from the region of glacier No.1 in the Tianshan Mountains, Xinjiang were studied by light microscope and SEM. The results indicated that the leaf apexes of these 10 species are acuminate or long-hair-shaped. The leaf apex cells are transparent, short or narrow. The leaf cell walls are thick, and the water conducting cells are larger. When the leaves of the plant are dry, the cell wall has different degree of conversity, and also some tiny holes on the surface of the most specie. The microstructures of Brachythecium B.S.G., Cirriphyllum Grout. and Rhynchostegium B.S.G. are different. The morphological features of leaves of the plant species in different genera and even in the same genera are different due to the different growing environment, which revealed that the microstructures of these 10 species are closely related to the growing environment. The results of this study could provide some information for the classification of Brachytheciaceae plant species in the region of Glacier No.1 in the Tianshan Mountains.

Key words: Brachytheciaceae, microstructure, SEM, glacier No.1, Xinjiang