Abstract:Karyotypes of 12 species of Paphiopedilum subgenus Paphiopedilum were studied by root tips squash method. The results showed that the chromosome number and karyotype were different among these species. The formulae were as follows: P. philippinense for 2n=2x=26=16m+10sm, P. dithanum for 2n=2x=26=20m+6sm, P. densissimum for 2n=2x=26=22m+4sm, P. parishii and P. hirsutissimum for 2n=2x=26=24m+2sm, P. henryanum, P. markianum and P. rhizomatosum for 2n=2x=26=26m, P. callosum for 2n=2x=32=2M+24m+6sm, P. microchilum for 2n=2x=38=28m+10sm, P. appletonianum and P. hainanensis for 2n=2x=38=30m+8sm. The diploid mainly consisted of metacentric chromosomes without satellites. The ratio of the longest chromosome to the shortest chromosome (Lc/Sc) ranged from 2.07 to 3.44. The percentage of chromosomes with arm ratio (P.C.A)＞2 ranged from 0 to 23.1%. The index of the karyotypic asymmetry (As.K) was from 53.50% to 58.95%. The karyotypes of P. henryanum, P. dithanum, P. densissimum, P. parishii, P. markianum and P. rhizomatosum were of Stebbins’s 1B type, and the others belong to 2B type.
