Abstract: There are five species of Isoetes in China, all of them are the first-grade state protection plants at the most endangered level (CR) of wild plants. From vegetative organ speaking, blade features become the most important basis for classification because of the simplified roots and stem in Isoetes. Because the height and leaf number of Isoetes hypsophila are significantly different from the others, the leaves epidermis of Isoetes sinensis, I.yunguiensis, I.taiwanensis and I.orientalis were observed by optical microscope. The results indicated that the rotation angle and pore distribution area are different, stomatal apparatus have upper uniformity; In different development periods, the stomatal index, pore distribution, height ratio of adaxial leaf surface and abaxial leaf surface have obvious taxonomy values, which provide a new basis for interspecific identification of Isoetes. In addition, this paper discussed the classification relationship in four Chinese Isoetes and first reported the heteroideus long strip cells.

Key words: Isoetaceae, leaf cuticle, classification characteristics