Abstract: By examining the somatic chromosome numbers and average numbers of bulbils per leaf of 10 populations belonging to 5 species of Pinellia, 5 chromosome numbers (P.peltata Pei 2n = 78, P. cordata N. E. Brown 2n= 72, P. ternata (Thunb.) Breit. 2n= 54,99,108) new to this genus are reported. The present work also shows that the species with x= 13 including P. yaoluopingensis X. H. Guo et X. L. Liu (popullation Ⅰ ～ Ⅲ ), P. tripartita (Blume) Schott (previous reports), P. pedatisecta Schott (population Ⅳ)and P. peltata (population Ⅴ )have no bulbils at all,while those with x= 9 including P. cordata (population Ⅵ ) and P. ternata (population Ⅶ ～ Ⅹ )have bulbils more or less depending on their ploidy－the average number of bulbils per leaf of hexaploid (population Ⅶ ) is only 0. 043,which is much lower than 1.95 of that of dodecaploids (population Ⅹ ). Based on these observations, it could be supposed that polyploidy reinforce apomixis, the diploid ancestors of P.ternata have no bulbils and in Pinellia, x= 13 may be more primitive than x = 9. The chromosome counts of the Araceae are changeable and complex, but appear to be explainable on the dual basis of ascending and descending dysploidy at secondary (paleopolyploid)level from a primitive basic number x = 7. P. ternata is a polyploid complex and probably it came from a diploid ancestors without bulbils and with x = 7,8,9, etc. The basic chromosome numbers x=7,8,9 of Pinellia ternata may have been derived from x= 13 of P. yaoluopingensis by descending dysploidy in the early stage of the evolution of this genus. Then, as a result of secondary polyploidy, bulbils which enable the species to adapt to its varied environments occur and they might lead to a more rapid evolution in this species.

Key words: Pinellia, Chromosome basic numbers, Ploidy, Bulbil occurrence