Abstract: The leaf structures of 17 mosses collected from different environmental conditions were transected and compared by means of paraffin wax section . The results showed that species vary much among the features such as the absence or presence of hydrome cells, the differentiation of steroid cells, the numbers of cell layer , the density of the costae, the numbers of laminal cell layer , etc . The leaf anatomical structures of the mosses are of ecological adaptation to their habitats . The mosses under dry conditions often have thickened laminal cell-walls on the surfaces , and some of them have appendiculate structures . The differentiation states of costae indicates the ways they absorb and transport water , and their ability adapting to the dry conditions, which was elucidated by the following examples: Brachythecium plumosum, because of its thin cell-walls in the costae and the absence of hydrome , assistant and steroid cells, can absorb water and nutrition under
shady and moist conditions ; Plagiomnium rostratum, though often grows in shady and wet condition , has hydrome and steroid cells, a feature similar to those of xeric mosses , which endows it to grow in the conditions with periodical drought stress during its life cycle ; Hygrohypnum luridum is characterized by its slender leaves with only one layer of cells , the thin cellwalls, the absence of filaments on the leaf surface, and the fewer layer cells in the costae, the absence of hydrome and steroid cells . These features make it adaptable to aquatic environments . For Pogonatum inflexum and Atrichum undulatum, their ventral surfaces covered with lamella, while for Racomitrium japonicum, Thuidium cymbifolium, Macromitrium ferriei, Diphyscium fulvifolium, Barbula unguiculata and Ceratodon purpureus, their leaves are strongly mammillose or papillos. Such appendiculate structures made them adaptable to dry conditions .

Key words: Mosses