Abstract: This paper deals with pollen morphology of Zizania L. and its relatives. A total of 7 genera, 13 species, 3 varieties and 1 form were examined under light microscope and scanning electron microscope. The results are as follows: 1. The genus Zizania belongs to tribe Oryzeae as shown by pollen characters, i, e. subspheroidal to ovoid in shape, monoporate, exine two-layered, with minute granules under LM. 2. The evolutionary trend of these taxa seems to be from minute granules free (Zizania latifolia, Z. texana, Zizaniopsis milicea and Oryza sativa) to minute granules aggregated in a group of 2-4 (many) (Zizania aquatica, Z. palustris, Leersia hexandra etc.). The genus Zizania may be derived from the ancient stock which has also given rise to the genus Oryza, and therefore parallel evolution may have taken place in Oryzeae, i. e. from perennial species to annual species in Zizania in one line, and from the genus Oryza to Leersia, Chikusichloa etc. in the other. 3. The characters of pollen morphology under LM and SEM support the division of the genus, Zizania into 4 species, 2 subspecies in the world, i. e. Z. latifolia (Griseb.) Turcz. ex Stapf, Z. texana Hitchc., Z. aquatica subsp. aquatica, Z. aquatica subsp. brevis (Fassett) S. L.Chen, Z. palustris subsp. palustris, and Z. palustris subsp. interior (Fassett) S. L. Chen.

Key words: Zizania L., Pollen morphology, Systematic evolution