Abstract: The karyotypes of Alisma species in Hubei were analysed. The authors have surveyed populations in fields, measured some morphological characters, made some experiments of cultivation, and further studied classificatory problems in this genus. The results are as follows: 1. There are three species in the provinc: A. plantago-aquatica L., A. orientale (Sam.) Juzep. and A. canaliculatum A. Br. Bouche. 2. A. plantago-aquatica and A. orientale are diploids, 2n=2x=14, A. canaliculatum is a hexaploid, 2n=6x=42. A new type of karyotype is reported here for A. orientale, which is contrary to the reports that the karyotypes of Alisma are uniform. 3. There are obvious differences between A. plantago-aquatica and A. orientale in morphology and karyotype and they should be regarded as two separate species. 4. There are three patterns of karyotype variation in this genus: ① Polyploidy; ② Variation of individual chromosomes from symmetry to asymmetry; ③ Increase of karyotype symmetry.

Key words: Alisma, Karyotype, Classification