Chromosome numbers and other karyological data of four Stemona species (Stemonaceae) from Thailand

Chromosome numbers and other karyological data of four Stemona spp. (Stemonaceae) from Thailand are reported. Three taxa (S. collinsae Craib, S. kerrii Craib and an unidentified species) exhibit 2n = 14 chromosomes, for S. curtisii Hook.f. a range of 2n = 13–16 was established. Based on the counts of c. 30% of the species of Stemona, x = 7 is very likely to be the basic number for the genus. Chromosome size and morphology of the investigated species are compared with literature data and show differences that might be of importance for infrageneric classification. In this connection the taxonomic position of the genus Pentastemona from Sumatra is also discussed.