Abstract: The identification of the photosynthetic pathway of 46 species from the Poaceae, Cypcraceae, Amaranthaceae and Asclepiadaceae were made using stable carbon isotope ratio measurements. 36 species showed the δ¹³C value of -10.43 to -13.66‰ and 1 species with succulent leaves had aδ¹³C value of -15.24‰. It is suggested that these species are new C₄ and CAM type plants, respectively.According to the mean δ¹³C value of three C₄ suhtypes proposed hy Hatteraley, it is possible that 8 species with δ¹³C value of -10.4 to -10.9‰ are NADP-ME type, and 6 species with δ¹³C value of-13‰ may be the NAD-ME type. The others will be NADP-ME or PCK type.